[leetcode] Path Sum

Posted 2020-09-30 lxjshuju

问题描写叙述：

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.

代码：

public class TreeNode {
	      int val;
	      TreeNode left;
	      TreeNode right;
	      TreeNode(int x) { val = x; }
	 }
	
	    public boolean hasPathSum(TreeNode root, int sum) {
	    	if(root == null)
	    		return false;
	    	
	    	 return getPathNum(root,sum);
	    	
	    	
	    	
	    }
	    
	    public boolean getPathNum(TreeNode root, int sum){
	    	if(root.left == null && root.right ==null){
	    		if(sum == root.val)
	    			return true;
	    		else return false;
	    		
	    	}
	    	
	    	
	    	boolean ltest = false;
	    	boolean rtest = false;
	    	
	    	if(root.left !=null)
	    		ltest = getPathNum(root.left, sum-root.val);
	    	if(root.right !=null)
	    		rtest = getPathNum(root.right, sum-root.val);
	    	
	    	return (ltest||rtest);
	    }