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feat: add solutions to lc problems: No.2859~2861 #1644

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yanglbme merged 1 commit into main from dev-new
Sep 18, 2023
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feat: add solutions to lc problems: No.2859~2861 
* No.2859.Sum of Values at Indices With K Set Bits
* No.2860.Happy Students
* No.2861.Maximum Number of Alloys
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yanglbme committed Sep 18, 2023
commit 40ff8358963dbd07190116f93c25f0ed21c3291c
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Original file line number Diff line number Diff line change
Expand Up @@ -58,14 +58,24 @@

<!-- 这里可写通用的实现逻辑 -->

**方法一:模拟**

我们直接遍历每个下标 $i,ドル判断其二进制表示中 1ドル$ 的个数是否等于 $k,ドル如果等于则将其对应的元素累加到答案 $ans$ 中。

遍历结束后,返回答案即可。

时间复杂度 $O(n \times \log n),ドル其中 $n$ 是数组 $nums$ 的长度。空间复杂度 $O(1)$。

<!-- tabs:start -->

### **Python3**

<!-- 这里可写当前语言的特殊实现逻辑 -->

```python

class Solution:
def sumIndicesWithKSetBits(self, nums: List[int], k: int) -> int:
return sum(x for i, x in enumerate(nums) if i.bit_count() == k)
```

### **Java**
Expand All @@ -89,13 +99,54 @@ class Solution {
### **C++**

```cpp

class Solution {
public:
int sumIndicesWithKSetBits(vector<int>& nums, int k) {
int ans = 0;
for (int i = 0; i < nums.size(); ++i) {
if (__builtin_popcount(i) == k) {
ans += nums[i];
}
}
return ans;
}
};
```

### **Go**

```go
func sumIndicesWithKSetBits(nums []int, k int) (ans int) {
for i, x := range nums {
if bits.OnesCount(uint(i)) == k {
ans += x
}
}
return
}
```

### **TypeScript**

```ts
function sumIndicesWithKSetBits(nums: number[], k: number): number {
let ans = 0;
for (let i = 0; i < nums.length; ++i) {
if (bitCount(i) === k) {
ans += nums[i];
}
}
return ans;
}

function bitCount(n: number): number {
let count = 0;
while (n) {
n &= n - 1;
count++;
}
return count;
}
```

### **...**
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Expand Up @@ -59,7 +59,9 @@ Hence, the answer is nums[3] = 1.
### **Python3**

```python

class Solution:
def sumIndicesWithKSetBits(self, nums: List[int], k: int) -> int:
return sum(x for i, x in enumerate(nums) if i.bit_count() == k)
```

### **Java**
Expand All @@ -81,13 +83,54 @@ class Solution {
### **C++**

```cpp

class Solution {
public:
int sumIndicesWithKSetBits(vector<int>& nums, int k) {
int ans = 0;
for (int i = 0; i < nums.size(); ++i) {
if (__builtin_popcount(i) == k) {
ans += nums[i];
}
}
return ans;
}
};
```

### **Go**

```go
func sumIndicesWithKSetBits(nums []int, k int) (ans int) {
for i, x := range nums {
if bits.OnesCount(uint(i)) == k {
ans += x
}
}
return
}
```

### **TypeScript**

```ts
function sumIndicesWithKSetBits(nums: number[], k: number): number {
let ans = 0;
for (let i = 0; i < nums.length; ++i) {
if (bitCount(i) === k) {
ans += nums[i];
}
}
return ans;
}

function bitCount(n: number): number {
let count = 0;
while (n) {
n &= n - 1;
count++;
}
return count;
}
```

### **...**
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@@ -0,0 +1,12 @@
class Solution {
public:
int sumIndicesWithKSetBits(vector<int>& nums, int k) {
int ans = 0;
for (int i = 0; i < nums.size(); ++i) {
if (__builtin_popcount(i) == k) {
ans += nums[i];
}
}
return ans;
}
};
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Original file line number Diff line number Diff line change
@@ -0,0 +1,8 @@
func sumIndicesWithKSetBits(nums []int, k int) (ans int) {
for i, x := range nums {
if bits.OnesCount(uint(i)) == k {
ans += x
}
}
return
}
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
class Solution:
def sumIndicesWithKSetBits(self, nums: List[int], k: int) -> int:
return sum(x for i, x in enumerate(nums) if i.bit_count() == k)
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Original file line number Diff line number Diff line change
@@ -0,0 +1,18 @@
function sumIndicesWithKSetBits(nums: number[], k: number): number {
let ans = 0;
for (let i = 0; i < nums.length; ++i) {
if (bitCount(i) === k) {
ans += nums[i];
}
}
return ans;
}

function bitCount(n: number): number {
let count = 0;
while (n) {
n &= n - 1;
count++;
}
return count;
}
71 changes: 69 additions & 2 deletions solution/2800-2899/2860.Happy Students/README.md
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Expand Up @@ -56,14 +56,40 @@

<!-- 这里可写通用的实现逻辑 -->

**方法一:排序 + 枚举**

假设选出了 $k$ 个学生,那么以下情况成立:

- 如果 $nums[i] = k,ドル那么不存在分组方法;
- 如果 $nums[i] \gt k,ドル那么学生 $i$ 不被选中;
- 如果 $nums[i] \lt k,ドル那么学生 $i$ 被选中。

因此,被选中的学生一定是排序后的 $nums$ 数组中的前 $k$ 个元素。

我们在 $[0,..n]$ 范围内枚举 $k,ドル对于当前选出的学生人数 $i,ドル我们可以得到组内最大的学生编号 $i-1,ドル数字为 $nums[i-1]$。如果 $i \gt 0$ 并且 $nums[i-1] \ge i,ドル那么不存在分组方法;如果 $i \lt n$ 并且 $nums[i] \le i,ドル那么不存在分组方法。否则,存在分组方法,答案加一。

枚举结束后,返回答案即可。

时间复杂度 $O(n \times \log n),ドル空间复杂度 $O(\log n)$。其中 $n$ 为数组长度。

<!-- tabs:start -->

### **Python3**

<!-- 这里可写当前语言的特殊实现逻辑 -->

```python

class Solution:
def countWays(self, nums: List[int]) -> int:
nums.sort()
n = len(nums)
ans = 0
for i in range(n + 1):
if i and nums[i - 1] >= i:
continue
if i < n and nums[i] <= i:
continue
return ans
```

### **Java**
Expand All @@ -89,13 +115,54 @@ class Solution {
### **C++**

```cpp

class Solution {
public:
int countWays(vector<int>& nums) {
sort(nums.begin(), nums.end());
int ans = 0;
int n = nums.size();
for (int i = 0; i <= n; ++i) {
if ((i && nums[i - 1] >= i) || (i < n && nums[i] <= i)) {
continue;
}
++ans;
}
return ans;
}
};
```

### **Go**

```go
func countWays(nums []int) (ans int) {
sort.Ints(nums)
n := len(nums)
for i := 0; i <= n; i++ {
if (i > 0 && nums[i-1] >= i) || (i < n && nums[i] <= i) {
continue
}
ans++
}
return
}
```

### **TypeScript**

```ts
function countWays(nums: number[]): number {
nums.sort((a, b) => a - b);
let ans = 0;
const n = nums.length;
for (let i = 0; i <= n; ++i) {
if ((i && nums[i - 1] >= i) || (i < n && nums[i] <= i)) {
continue;
}
++ans;
}
return ans;
}
```

### **...**
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55 changes: 53 additions & 2 deletions solution/2800-2899/2860.Happy Students/README_EN.md
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Expand Up @@ -55,7 +55,17 @@ The class teacher selects all the students to form the group.
### **Python3**

```python

class Solution:
def countWays(self, nums: List[int]) -> int:
nums.sort()
n = len(nums)
ans = 0
for i in range(n + 1):
if i and nums[i - 1] >= i:
continue
if i < n and nums[i] <= i:
continue
return ans
```

### **Java**
Expand All @@ -79,13 +89,54 @@ class Solution {
### **C++**

```cpp

class Solution {
public:
int countWays(vector<int>& nums) {
sort(nums.begin(), nums.end());
int ans = 0;
int n = nums.size();
for (int i = 0; i <= n; ++i) {
if ((i && nums[i - 1] >= i) || (i < n && nums[i] <= i)) {
continue;
}
++ans;
}
return ans;
}
};
```

### **Go**

```go
func countWays(nums []int) (ans int) {
sort.Ints(nums)
n := len(nums)
for i := 0; i <= n; i++ {
if (i > 0 && nums[i-1] >= i) || (i < n && nums[i] <= i) {
continue
}
ans++
}
return
}
```

### **TypeScript**

```ts
function countWays(nums: number[]): number {
nums.sort((a, b) => a - b);
let ans = 0;
const n = nums.length;
for (let i = 0; i <= n; ++i) {
if ((i && nums[i - 1] >= i) || (i < n && nums[i] <= i)) {
continue;
}
++ans;
}
return ans;
}
```

### **...**
Expand Down
15 changes: 15 additions & 0 deletions solution/2800-2899/2860.Happy Students/Solution.cpp
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@@ -0,0 +1,15 @@
class Solution {
public:
int countWays(vector<int>& nums) {
sort(nums.begin(), nums.end());
int ans = 0;
int n = nums.size();
for (int i = 0; i <= n; ++i) {
if ((i && nums[i - 1] >= i) || (i < n && nums[i] <= i)) {
continue;
}
++ans;
}
return ans;
}
};
11 changes: 11 additions & 0 deletions solution/2800-2899/2860.Happy Students/Solution.go
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@@ -0,0 +1,11 @@
func countWays(nums []int) (ans int) {
sort.Ints(nums)
n := len(nums)
for i := 0; i <= n; i++ {
if (i > 0 && nums[i-1] >= i) || (i < n && nums[i] <= i) {
continue
}
ans++
}
return
}
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