0112-path-sum.java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    //This would be easily solved by DFS and then comparing the values
    public boolean dfs(TreeNode root, int targetSum, int currSum){
        if(root == null) return false;

        currSum += root.val;
        if(root.left == null && root.right == null){
            return (currSum == targetSum);
        }
        return dfs(root.left, targetSum, currSum) || dfs(root.right, targetSum, currSum);
    }
    public boolean hasPathSum(TreeNode root, int targetSum) {
        return dfs(root, targetSum, 0);
    }
}