437. Path Sum III

#### QUESTION:

You are given a binary tree in which each node contains an integer value.

Find the number of paths that sum to a given value.

The path does not need to start or end at the root or a leaf, but it must go downwards (traveling only from parent nodes to child nodes).

The tree has no more than 1,000 nodes and the values are in the range -1,000,000 to 1,000,000.

Example:

``````root = [10,5,-3,3,2,null,11,3,-2,null,1], sum = 8

10
/  \
5   -3
/ \    \
3   2   11
/ \   \
3  -2   1

Return 3. The paths that sum to 8 are:

1.  5 -> 3
2.  5 -> 2 -> 1
3. -3 -> 11
``````

#### SOLUTION:

``````public class Solution {
public int pathSumIIIResult = 0;
public int pathSum(TreeNode root, int sum) {
if(root == null) return pathSumIIIResult;
Stack<Integer> stack = new Stack<>();
pathSumIII(root,sum,stack);
return pathSumIIIResult;
}

public void pathSumIII(TreeNode root,int sum , Stack<Integer> stack){
stack.push(root.val);
int he = 0;
for(int i = stack.size()-1;i>=0;i--){
int value = stack.elementAt(i);
he+=value;
if(he == sum)
pathSumIIIResult++;
}
if(root.left != null) pathSumIII(root.left,sum,stack);
if(root.right != null) pathSumIII(root.right,sum,stack);
stack.pop();
}
}
``````
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