leecode112.路径总和

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool hasPathSum(TreeNode* root, int targetSum) {
        if(root==NULL)//在示例三中这种情况直接false，后续不可能再执行这个条件的语句，因为在判断为叶子结点的时候递归已经停止
            return false;
        else{
            if(root->left==NULL&&root->right==NULL)
                if(targetSum-root->val==0)
                    return true;
                else 
                    return false;
            else
                return hasPathSum(root->left,targetSum-root->val)||hasPathSum(root->right,targetSum-root->val);
        }
    }
};