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Commit 677dae5

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feat: add solutions to leetcode problem: No.0494. Target Sum
1 parent 9c2b71e commit 677dae5

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4 files changed

+142
-15
lines changed

4 files changed

+142
-15
lines changed

‎solution/0400-0499/0494.Target Sum/README.md‎

Lines changed: 52 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -42,12 +42,12 @@
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<!-- 这里可写通用的实现逻辑 -->
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类似背包问题,只不过下标可能会出现负数,需要特殊处理。
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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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```
@@ -57,7 +57,57 @@
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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 findTargetSumWays(int[] nums, int target) {
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if (target < -1000 || target > 1000) {
63+
return 0;
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}
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int n = nums.length;
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int[][] dp = new int[n][2001];
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dp[0][nums[0] + 1000] = 1;
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dp[0][-nums[0] + 1000] += 1;
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for (int i = 1; i < n; i++) {
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for (int j = -1000; j <= 1000; j++) {
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if (dp[i - 1][j + 1000] > 0) {
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dp[i][j + nums[i] + 1000] += dp[i - 1][j + 1000];
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dp[i][j - nums[i] + 1000] += dp[i - 1][j + 1000];
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}
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}
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}
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return dp[n - 1][target + 1000];
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}
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}
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```
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### **Go**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```go
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func findTargetSumWays(nums []int, target int) int {
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if target < -1000 || target > 1000 {
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return 0
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}
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n := len(nums)
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dp := make([][]int, n)
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for i := 0; i < n; i++ {
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dp[i] = make([]int, 2001)
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}
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dp[0][nums[0]+1000] += 1
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dp[0][-nums[0]+1000] += 1
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for i := 1; i < n; i++ {
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for j := -1000; j <= 1000; j++ {
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if dp[i-1][j+1000] > 0 {
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dp[i][j+nums[i]+1000] += dp[i-1][j+1000]
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dp[i][j-nums[i]+1000] += dp[i-1][j+1000]
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}
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}
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}
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return dp[n-1][target+1000]
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}
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```
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### **...**

‎solution/0400-0499/0494.Target Sum/README_EN.md‎

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Original file line numberDiff line numberDiff line change
@@ -48,6 +48,8 @@
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## Solutions
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It is similar to the backpack problem, except that the index may appear negative, which requires special handling.
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<!-- tabs:start -->
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### **Python3**
@@ -59,7 +61,55 @@
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### **Java**
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```java
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class Solution {
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public int findTargetSumWays(int[] nums, int target) {
66+
if (target < -1000 || target > 1000) {
67+
return 0;
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}
69+
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int n = nums.length;
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int[][] dp = new int[n][2001];
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dp[0][nums[0] + 1000] = 1;
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dp[0][-nums[0] + 1000] += 1;
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for (int i = 1; i < n; i++) {
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for (int j = -1000; j <= 1000; j++) {
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if (dp[i - 1][j + 1000] > 0) {
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dp[i][j + nums[i] + 1000] += dp[i - 1][j + 1000];
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dp[i][j - nums[i] + 1000] += dp[i - 1][j + 1000];
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}
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}
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}
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return dp[n - 1][target + 1000];
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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 findTargetSumWays(nums []int, target int) int {
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if target < -1000 || target > 1000 {
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return 0
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}
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n := len(nums)
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dp := make([][]int, n)
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for i := 0; i < n; i++ {
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dp[i] = make([]int, 2001)
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}
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dp[0][nums[0]+1000] += 1
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dp[0][-nums[0]+1000] += 1
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for i := 1; i < n; i++ {
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for j := -1000; j <= 1000; j++ {
105+
if dp[i-1][j+1000] > 0 {
106+
dp[i][j+nums[i]+1000] += dp[i-1][j+1000]
107+
dp[i][j-nums[i]+1000] += dp[i-1][j+1000]
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}
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}
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}
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return dp[n-1][target+1000]
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}
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```
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### **...**
Lines changed: 21 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,21 @@
1+
func findTargetSumWays(nums []int, target int) int {
2+
if target < -1000 || target > 1000 {
3+
return 0
4+
}
5+
n := len(nums)
6+
dp := make([][]int, n)
7+
for i := 0; i < n; i++ {
8+
dp[i] = make([]int, 2001)
9+
}
10+
dp[0][nums[0]+1000] += 1
11+
dp[0][-nums[0]+1000] += 1
12+
for i := 1; i < n; i++ {
13+
for j := -1000; j <= 1000; j++ {
14+
if dp[i-1][j+1000] > 0 {
15+
dp[i][j+nums[i]+1000] += dp[i-1][j+1000]
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dp[i][j-nums[i]+1000] += dp[i-1][j+1000]
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}
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}
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}
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return dp[n-1][target+1000]
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}
Lines changed: 19 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -1,17 +1,23 @@
11
class Solution {
2-
public int findTargetSumWays(int[] nums, int S) {
3-
int[] ans = new int[1];
4-
wayDfs(nums, 0, S, ans);
5-
return ans[0];
6-
}
7-
8-
private void wayDfs(int[] nums, int start, int left, int[] ans) {
9-
if (start == nums.length) {
10-
if (left == 0) ans[0]++;
11-
return;
2+
public int findTargetSumWays(int[] nums, int target) {
3+
if (target < -1000 || target > 1000) {
4+
return 0;
125
}
136

14-
wayDfs(nums, start + 1, left + nums[start], ans);
15-
wayDfs(nums, start + 1, left - nums[start], ans);
7+
int n = nums.length;
8+
int[][] dp = new int[n][2001];
9+
10+
dp[0][nums[0] + 1000] = 1;
11+
dp[0][-nums[0] + 1000] += 1;
12+
13+
for (int i = 1; i < n; i++) {
14+
for (int j = -1000; j <= 1000; j++) {
15+
if (dp[i - 1][j + 1000] > 0) {
16+
dp[i][j + nums[i] + 1000] += dp[i - 1][j + 1000];
17+
dp[i][j - nums[i] + 1000] += dp[i - 1][j + 1000];
18+
}
19+
}
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}
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return dp[n - 1][target + 1000];
1622
}
17-
}
23+
}

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