You are given a binary tree in which each node contains an integer value.
Find the number of paths that sum to a given value.
The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to child nodes).
The tree has no more than 1,000 nodes and the values are in the range -1,000,000 to 1,000,000.
Example:
root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8
10
/ \
5 -3
/ \ \
3 2 11
/ \ \
3 -2 1
Return 3. The paths that sum to 8 are:
1. 5 -> 3
2. 5 -> 2 -> 1
3. -3 -> 11
Solution 1
/**
* Definition for a binary tree node.
* function TreeNode(val) {
* this.val = val;
* this.left = this.right = null;
* }
*/
/**
* Traverse the binary tree with Depth-First Search (DFS) algorithm (preorder)
* @param {TreeNode} root
* @param {number} sum
* @return {number}
*/
var pathSum = function(root, sum) {
"use strict";
let result = 0;
function findPath(node, tmpSum) {
if (node) {
tmpSum += node.val;
if (tmpSum === sum) {
result++;
}
findPath(node.left, tmpSum);
findPath(node.right, tmpSum);
}
}
function dfs(node) {
if (node) {
findPath(node, 0);
dfs(node.left);
dfs(node.right);
}
}
dfs(root);
return result;
};Solution 2
/**
* Definition for a binary tree node.
* function TreeNode(val) {
* this.val = val;
* this.left = this.right = null;
* }
*/
/**
* Traverse the binary tree with Depth-First Search (DFS) algorithm (preorder)
* @param {TreeNode} root
* @param {number} sum
* @return {number}
*/
var pathSum = function(root, sum) {
"use strict";
let result = 0;
function dfs(node, pathSum, table) {
if (node) {
pathSum += node.val;
if (table[pathSum-sum]) {
result += table[pathSum-sum];
}
if (table[pathSum] === undefined) {
table[pathSum] = 0;
}
table[pathSum]++;
dfs(node.left, pathSum, table);
dfs(node.right, pathSum, table);
table[pathSum]--;
}
}
dfs(root, 0, { 0: 1 });
return result;
};