首页 > 代码库 > Path Sum

Path Sum

2024-07-07 05:45:54   228人阅读

题目

Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.

For example:
Given the below binary tree and sum = 22,
              5
             /             4   8
           /   /           11  13  4
         /  \              7    2      1

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

方法

本质是树的遍历，使用树的先序遍历，并使用一个变量tempSum来记录遍历到当前结点的和。

	public boolean preOrder(TreeNode node, int sum, int tempSum) {
		if (node != null) {
			tempSum += node.val;
			if (node.left == null && node.right == null) {
				if (tempSum == sum) {
					return true;
				} else {
					return false;
				}
			}
			
			return preOrder(node.left, sum, tempSum) || preOrder(node.right, sum, tempSum);
		} 
		return false;

	}
	
    public boolean hasPathSum(TreeNode root, int sum) {
    	 return preOrder(root, sum, 0);
    }


联系
我们