g0401_0500.s0437_path_sum_iii.Solution Maven / Gradle / Ivy
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Java-based LeetCode algorithm problem solutions, regularly updated
package g0401_0500.s0437_path_sum_iii;
// #Medium #Top_100_Liked_Questions #Depth_First_Search #Tree #Binary_Tree #Level_2_Day_7_Tree
// #Big_O_Time_O(n)_Space_O(n) #2022_07_16_Time_18_ms_(45.66%)_Space_42_MB_(88.96%)
import com_github_leetcode.TreeNode;
/*
* 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;
* }
* }
*/
public class Solution {
private int count = 0;
public int pathSum(TreeNode root, int targetSum) {
if (root == null) {
return 0;
}
helper(root, targetSum, 0);
pathSum(root.left, targetSum);
pathSum(root.right, targetSum);
return count;
}
public void helper(TreeNode node, int targetSum, long currSum) {
currSum += node.val;
if (targetSum == currSum) {
count++;
}
if (node.left != null) {
helper(node.left, targetSum, currSum);
}
if (node.right != null) {
helper(node.right, targetSum, currSum);
}
}
}