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Commit 469f340

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feat: add solutions to lc problem: No.1664
No.1664.Ways to Make a Fair Array
1 parent efbce23 commit 469f340

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6 files changed

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6 files changed

+318
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‎solution/1600-1699/1664.Ways to Make a Fair Array/README.md‎

Lines changed: 121 additions & 1 deletion
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@@ -64,22 +64,142 @@
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<!-- 这里可写通用的实现逻辑 -->
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**方法一:预处理 + 枚举**
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我们先预处理得到数组 `nums` 的奇数下标元素之和 $x$ 以及偶数下标元素之和 $y$。
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然后从前往后枚举数组 `nums` 的每个元素 $v,ドル用变量 $a$ 和 $b$ 分别记录已遍历的奇数下标元素之和以及偶数下标元素之和。
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我们观察发现,对于当前遍历到的元素 $v,ドル如果删除了,那么该元素之后的奇偶下标元素之和会发生交换。此时,我们先判断该位置下标 $i$ 是奇数还是偶数。
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如果是奇数下标,删除该元素后,数组的偶数下标元素之和为 $x-v-a+b,ドル而奇数下标元素之和为 $y-b+a,ドル如果这两个和相等,那么就是一个平衡数组,答案加一。
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如果是偶数下标,删除该元素后,数组的奇数下标元素之和为 $y-v-b+a,ドル而偶数下标元素之和为 $x-a+b,ドル如果这两个和相等,那么就是一个平衡数组,答案加一。
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然后我们更新 $a$ 和 $b,ドル继续遍历下一个元素。
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遍历完数组后,即可得到答案。
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时间复杂度 $O(n),ドル空间复杂度 $O(1)$。其中 $n$ 为数组的长度。
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<!-- tabs:start -->
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### **Python3**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```python
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class Solution:
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def waysToMakeFair(self, nums: List[int]) -> int:
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x, y = sum(nums[1::2]), sum(nums[::2])
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ans = 0
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a = b = 0
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for i, v in enumerate(nums):
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if (i & 1) and x - v - a + b == y - b + a:
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ans += 1
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elif (i & 1) == 0 and y - v - b + a == x - a + b:
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ans += 1
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if i & 1:
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a += v
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else:
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b += v
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return ans
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```
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### **Java**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```java
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class Solution {
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public int waysToMakeFair(int[] nums) {
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int n = nums.length;
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int x = 0, y = 0;
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for (int i = 0; i < n; ++i) {
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if (i % 2 == 1) {
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x += nums[i];
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} else {
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y += nums[i];
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}
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}
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int ans = 0;
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int a = 0, b = 0;
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for (int i = 0; i < n; ++i) {
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int v = nums[i];
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if (i % 2 == 1 && x - v - a + b == y - b + a) {
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++ans;
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} else if (i % 2 == 0 && y - v - b + a == x - a + b) {
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++ans;
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}
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if (i % 2 == 1) {
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a += v;
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} else {
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b += v;
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}
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}
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return ans;
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int waysToMakeFair(vector<int>& nums) {
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int n = nums.size();
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int x = 0, y = 0;
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for (int i = 0; i < n; ++i) {
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if (i & 1)
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x += nums[i];
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else
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y += nums[i];
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}
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int ans = 0;
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int a = 0, b = 0;
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for (int i = 0; i < n; ++i) {
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int v = nums[i];
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if (i % 2 == 1 && x - v - a + b == y - b + a) ++ans;
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if (i % 2 == 0 && y - v - b + a == x - a + b) ++ans;
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if (i % 2 == 1)
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a += v;
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else
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b += v;
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}
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return ans;
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}
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};
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```
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### **Go**
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```go
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func waysToMakeFair(nums []int) (ans int) {
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x, y := 0, 0
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for i, v := range nums {
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if i%2 == 1 {
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x += v
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} else {
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y += v
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}
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}
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a, b := 0, 0
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for i, v := range nums {
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if i%2 == 1 && x-v-a+b == y-b+a {
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ans++
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}
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if i%2 == 0 && y-v-b+a == x-a+b {
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ans++
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}
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if i%2 == 1 {
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a += v
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} else {
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b += v
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}
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}
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return
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}
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```
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### **...**

‎solution/1600-1699/1664.Ways to Make a Fair Array/README_EN.md‎

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Original file line numberDiff line numberDiff line change
@@ -63,13 +63,115 @@ There is 1 index that you can remove to make nums fair.
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### **Python3**
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```python
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class Solution:
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def waysToMakeFair(self, nums: List[int]) -> int:
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x, y = sum(nums[1::2]), sum(nums[::2])
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ans = 0
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a = b = 0
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for i, v in enumerate(nums):
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if (i & 1) and x - v - a + b == y - b + a:
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ans += 1
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elif (i & 1) == 0 and y - v - b + a == x - a + b:
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ans += 1
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if i & 1:
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a += v
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else:
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b += v
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return ans
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```
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### **Java**
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```java
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class Solution {
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public int waysToMakeFair(int[] nums) {
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int n = nums.length;
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int x = 0, y = 0;
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for (int i = 0; i < n; ++i) {
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if (i % 2 == 1) {
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x += nums[i];
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} else {
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y += nums[i];
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}
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}
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int ans = 0;
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int a = 0, b = 0;
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for (int i = 0; i < n; ++i) {
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int v = nums[i];
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if (i % 2 == 1 && x - v - a + b == y - b + a) {
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++ans;
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} else if (i % 2 == 0 && y - v - b + a == x - a + b) {
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++ans;
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}
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if (i % 2 == 1) {
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a += v;
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} else {
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b += v;
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}
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}
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return ans;
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int waysToMakeFair(vector<int>& nums) {
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int n = nums.size();
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int x = 0, y = 0;
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for (int i = 0; i < n; ++i) {
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if (i & 1)
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x += nums[i];
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else
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y += nums[i];
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}
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int ans = 0;
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int a = 0, b = 0;
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for (int i = 0; i < n; ++i) {
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int v = nums[i];
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if (i % 2 == 1 && x - v - a + b == y - b + a) ++ans;
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if (i % 2 == 0 && y - v - b + a == x - a + b) ++ans;
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if (i % 2 == 1)
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a += v;
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else
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b += v;
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}
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return ans;
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}
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};
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```
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### **Go**
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```go
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func waysToMakeFair(nums []int) (ans int) {
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x, y := 0, 0
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for i, v := range nums {
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if i%2 == 1 {
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x += v
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} else {
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y += v
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}
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}
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a, b := 0, 0
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for i, v := range nums {
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if i%2 == 1 && x-v-a+b == y-b+a {
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ans++
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}
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if i%2 == 0 && y-v-b+a == x-a+b {
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ans++
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}
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if i%2 == 1 {
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a += v
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} else {
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b += v
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}
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}
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return
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}
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```
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### **...**
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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,25 @@
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class Solution {
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public:
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int waysToMakeFair(vector<int>& nums) {
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int n = nums.size();
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int x = 0, y = 0;
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for (int i = 0; i < n; ++i) {
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if (i & 1)
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x += nums[i];
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else
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y += nums[i];
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}
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int ans = 0;
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int a = 0, b = 0;
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for (int i = 0; i < n; ++i) {
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int v = nums[i];
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if (i % 2 == 1 && x - v - a + b == y - b + a) ++ans;
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if (i % 2 == 0 && y - v - b + a == x - a + b) ++ans;
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if (i % 2 == 1)
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a += v;
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else
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b += v;
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}
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return ans;
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}
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};
Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,25 @@
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func waysToMakeFair(nums []int) (ans int) {
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x, y := 0, 0
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for i, v := range nums {
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if i%2 == 1 {
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x += v
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} else {
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y += v
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}
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}
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a, b := 0, 0
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for i, v := range nums {
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if i%2 == 1 && x-v-a+b == y-b+a {
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ans++
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}
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if i%2 == 0 && y-v-b+a == x-a+b {
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ans++
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}
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if i%2 == 1 {
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a += v
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} else {
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b += v
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}
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}
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return
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}
Lines changed: 29 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,29 @@
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class Solution {
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public int waysToMakeFair(int[] nums) {
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int n = nums.length;
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int x = 0, y = 0;
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for (int i = 0; i < n; ++i) {
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if (i % 2 == 1) {
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x += nums[i];
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} else {
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y += nums[i];
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}
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}
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int ans = 0;
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int a = 0, b = 0;
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for (int i = 0; i < n; ++i) {
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int v = nums[i];
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if (i % 2 == 1 && x - v - a + b == y - b + a) {
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++ans;
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} else if (i % 2 == 0 && y - v - b + a == x - a + b) {
19+
++ans;
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}
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if (i % 2 == 1) {
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a += v;
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} else {
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b += v;
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}
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}
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return ans;
28+
}
29+
}
Lines changed: 15 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,15 @@
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class Solution:
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def waysToMakeFair(self, nums: List[int]) -> int:
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x, y = sum(nums[1::2]), sum(nums[::2])
4+
ans = 0
5+
a = b = 0
6+
for i, v in enumerate(nums):
7+
if (i & 1) and x - v - a + b == y - b + a:
8+
ans += 1
9+
elif (i & 1) == 0 and y - v - b + a == x - a + b:
10+
ans += 1
11+
if i & 1:
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a += v
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else:
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b += v
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return ans

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