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: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.
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int flag=0;
bool hasPathSum(TreeNode *root, int sum) {
if(root==NULL) return false;
pathSum(root,0,sum);
if(flag==1)
return true;
else
return false;
}
int pathSum(TreeNode *root,int res,int sum)
{
if(root==NULL) return 0;
res+=root->val;
int l=pathSum(root->left,res,sum);
int r=pathSum(root->right,res,sum);
if((l+r)==0&&res==sum)
{
flag=1;
}
}
};
原文：http://blog.csdn.net/u013011841/article/details/41532683