Merge pull request #2815 from titanwings/master

添加目标和 go 回溯版本

Author: youngyangyang04

problems/0494.目标和.md

@@ -706,6 +706,31 @@ class Solution:
 ```
 
 ### Go
+回溯法思路
+```go
+func findTargetSumWays(nums []int, target int) int {
+    var result int
+    var backtracking func(nums []int, target int, index int, currentSum int)
+
+    backtracking = func(nums []int, target int, index int, currentSum int) {
+        if index == len(nums) {
+            if currentSum == target {
+                result++
+            }
+            return
+        }
+        
+        // 选择加上当前数字
+        backtracking(nums, target, index+1, currentSum+nums[index])
+        
+        // 选择减去当前数字
+        backtracking(nums, target, index+1, currentSum-nums[index])
+    }
+
+    backtracking(nums, target, 0, 0)
+    return result
+}
+```
 二维dp
 ```go
 func findTargetSumWays(nums []int, target int) int {