# 611. Valid Triangle Number

611. Valid Triangle Number

```class Solution {
public int triangleNumber(int[] nums) {
int count = 0;
for (int i = 0; i < nums.length; i++) {
for (int j = i+1; j < nums.length; j++) {
for (int k = j+1; k  nums[k] &&
nums[i] + nums[k] > nums[j]&&
nums[j] + nums[k] > nums[i]) {
count++;
}
}
}
}
return count;
}
}
```

# 653. Two Sum IV – Input is a BST

653. Two Sum IV – Input is a BST

```/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
class Solution {
public boolean findTarget(TreeNode root, int k) {
ArrayList data = new ArrayList();
traverers(root, data);
for (int i  = 0 ; i < data.size() ; i++)
for (int j  = 0 ; j < data.size() && i!=j ; j++)
if (data.get(i) + data.get(j) == k)
return true;

return false;
}

private void traverers(TreeNode root, ArrayList data) {
if (root != null) {
traverers(root.left, data);
traverers(root.right, data);
}
}
}
```

# 590. N-ary Tree Postorder Traversal

590. N-ary Tree Postorder Traversal

```/*
// Definition for a Node.
class Node {
public int val;
public List children;

public Node() {}

public Node(int _val,List _children) {
val = _val;
children = _children;
}
};
*/
class Solution {
public List postorder(Node root) {
List out = new ArrayList();
postorder(root, out);
return out;
}

private void postorder(Node root, List out) {
if( null != root){
for (int i = 0; i < root.children.size(); i++)
postorder(root.children.get(i), out);