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Description
/**
* Definition for a binary tree node.
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
*/
/**
* @param {TreeNode} root
* @param {number} targetSum
* @return {boolean}
*/
var hasPathSum = function (root, targetSum) {
const pathSum = (node, sum) => {
if (node === null) return false; // 节点为空, 返回false
if (node.left === null && node.right === null) { // 到达了叶子节点, 也就是路径的终点, 判断是否满足
return sum + node.val === targetSum;
}
sum += node.val; // 累加
return pathSum(node.left, sum) || pathSum(node.right, sum) // 左右子树 || 的关系
}
return pathSum(root, 0)
};