C++ | Leetcode C++题解之第437题路径总和III

题目：

题解：

class Solution {
public:unordered_map<long long, int> prefix;int dfs(TreeNode *root, long long curr, int targetSum) {if (!root) {return 0;}int ret = 0;curr += root->val;if (prefix.count(curr - targetSum)) {ret = prefix[curr - targetSum];}prefix[curr]++;ret += dfs(root->left, curr, targetSum);ret += dfs(root->right, curr, targetSum);prefix[curr]--;return ret;}int pathSum(TreeNode* root, int targetSum) {prefix[0] = 1;return dfs(root, 0, targetSum);}
};