Merge pull request #2727 from markwang1992/494-findTargetSumWays

494.目标和增加Go二维dp解法

problems/0494.目标和.md

@@ -706,6 +706,57 @@ class Solution:
 ```
 
 ### Go
+二维dp
+```go
+func findTargetSumWays(nums []int, target int) int {
+    sum := 0
+    for _, v := range nums {
+        sum += v
+    }
+    if math.Abs(float64(target)) > float64(sum) {
+        return 0 // 此时没有方案
+    }
+    if (target + sum) % 2 == 1 {
+        return 0 // 此时没有方案
+    }
+    bagSize := (target + sum) / 2
+    
+    dp := make([][]int, len(nums))
+    for i := range dp {
+        dp[i] = make([]int, bagSize + 1)
+    }
+    
+    // 初始化最上行
+    if nums[0] <= bagSize {
+        dp[0][nums[0]] = 1
+    }
+    
+    // 初始化最左列，最左列其他数值在递推公式中就完成了赋值
+    dp[0][0] = 1
+    
+    var numZero float64
+    for i := range nums {
+        if nums[i] == 0 {
+            numZero++
+        }
+        dp[i][0] = int(math.Pow(2, numZero))
+    }
+    
+    // 以下遍历顺序行列可以颠倒
+    for i := 1; i < len(nums); i++ { // 行，遍历物品
+        for j := 0; j <= bagSize; j++ { // 列，遍历背包
+            if nums[i] > j {
+                dp[i][j] = dp[i-1][j]
+            } else {
+                dp[i][j] = dp[i-1][j] + dp[i-1][j-nums[i]]
+            }
+        }
+    }
+    return dp[len(nums)-1][bagSize]
+}
+```
+
+一维dp
 ```go
 func findTargetSumWays(nums []int, target int) int {
 	sum := 0