Path Sum Solutions in C++

// Source : https://oj.leetcode.com/problems/path-sum/
// Author : Hao Chen
// Date   : 2014-06-22



#include <time.h>

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    Solution(){
        srand(time(NULL));
    }
    bool hasPathSum(TreeNode *root, int sum) {
        return hasPathSum3(root, sum, 0);
        return hasPathSum2(root, sum);
        return hasPathSum1(root, sum);    
    }

    bool hasPathSum3(TreeNode* root, int sum, int s) {
        if ( root == NULL) return false;
        s += root->val;
        if ( !root->left && !root->right)  return s == sum;
        return (hasPathSum3(root->left, sum, s) || hasPathSum3(root->right, sum, s));
    }
    
    bool hasPathSum1(TreeNode *root, int sum) {
        if (root==NULL) return false;
        vector<TreeNode*> v;
        v.push_back(root);
        while(v.size()>0){
            TreeNode* node = v.back();
            v.pop_back();
            if (node->left==NULL && node->right==NULL){
                if (node->val == sum){
                    return true;
                }
            }
            if (node->left){
                node->left->val += node->val;
                v.push_back(node->left);
            }
            if (node->right){
                node->right->val += node->val;
                v.push_back(node->right);
            }
        }
        return false;
        
    }
    
    bool hasPathSum2(TreeNode *root, int sum) {
        
        if (root==NULL) return false;
        
        if (root->left==NULL && root->right==NULL ){
            return (root->val==sum);
        }
        
        if (root->left){
            root->left->val += root->val;
            if (hasPathSum2(root->left, sum)){
                return true;
            }
        }
        
        if (root->right){
            root->right->val += root->val;
            if (hasPathSum2(root->right, sum)){
                return true;
            }
        }
        
        return false;
    }

};

#include <cstddef>
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
 
class Solution {
public:
    bool hasPathSum(TreeNode *root, int sum) {
        if (!root) return false;
        if (!root->left and !root->right and sum-root->val==0) return true;
        return hasPathSum(root->left, sum-root->val) or hasPathSum(root->right, sum-root->val); 
    }
};

/// Source : https://leetcode.com/problems/path-sum/description/
/// Author : liuyubobobo
/// Time   : 2017-11-17

#include <iostream>

using namespace std;

/// Definition for a binary tree node.
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};


/// Recursive
/// Time Complexity: O(n), where n is the nodes' number of the tree
/// Space Complexity: O(h), where h is the height of the tree
class Solution {
public:
    bool hasPathSum(TreeNode* root, int sum) {

        if(!root)
            return false;

        if(!root->left && !root->right)
            return sum == root->val;

        return hasPathSum(root->left, sum - root->val)
                || hasPathSum(root->right, sum - root->val);
    }
};


int main() {

    return 0;
}

/// Source : https://leetcode.com/problems/path-sum/description/
/// Author : liuyubobobo
/// Time   : 2018-11-17

#include <iostream>
#include <stack>

using namespace std;

/// Definition for a binary tree node.
struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};


/// Non-Recursive
/// Using Stack
///
/// Time Complexity: O(n), where n is the nodes' number of the tree
/// Space Complexity: O(h), where h is the height of the tree
class Solution {
public:
    bool hasPathSum(TreeNode* root, int sum) {

        if(!root)
            return false;

        stack<pair<TreeNode*, int>> stack;
        stack.push(make_pair(root, sum));
        while(!stack.empty()){
            TreeNode* cur = stack.top().first;
            int num = stack.top().second;
            stack.pop();

            if(num == cur->val && !cur->left && !cur->right)
                return true;

            if (cur->left)
                stack.push(make_pair(cur->left, num - cur->val));
            if (cur->right)
                stack.push(make_pair(cur->right, num - cur->val));
        }
        return false;
    }
};


int main() {

    return 0;
}