Java | Leetcode Java题解之第437题路径总和III
题目：
题解：
class Solution {
public int pathSum(TreeNode root, int targetSum) {
Map<Long, Integer> prefix = new HashMap<Long, Integer>();
prefix.put(0L, 1);
return dfs(root, prefix, 0, targetSum);
}
public int dfs(TreeNode root, Map<Long, Integer> prefix, long curr, int targetSum) {
if (root == null) {
return 0;
}
int ret = 0;
curr += root.val;
ret = prefix.getOrDefault(curr - targetSum, 0);
prefix.put(curr, prefix.getOrDefault(curr, 0) + 1);
ret += dfs(root.left, prefix, curr, targetSum);
ret += dfs(root.right, prefix, curr, targetSum);
prefix.put(curr, prefix.getOrDefault(curr, 0) - 1);
return ret;
}
}原文地址：https://blog.csdn.net/m0_57195758/article/details/142537147
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