135. ChildernSumPrperty..cpp

#include <bits/stdc++.h> 
/*************************************************************

    Following is the Binary Tree node structure

    class BinaryTreeNode
    {
    public :
        T data;
        BinaryTreeNode < T > *left;
        BinaryTreeNode < T > *right;

        BinaryTreeNode(T data) {
            this -> data = data;
            left = NULL;
            right = NULL;
        }
    };

*************************************************************/
void changeTree(BinaryTreeNode < int > * root) {
    if(root==NULL)return;

    int child = 0;
    if(root->left)child+=root->left->data;
    if(root->right)child+=root->right->data;

    if(child>=root->data)root->data = child;
    else{
        if(root->left)root->left->data = root->data;
        else if(root->right)root->right->data = root->data;
    }

    changeTree(root->left);
    changeTree(root->right);

    int total = 0;
    if(root->left)total += root->left->data;
    if(root->right)total += root->right->data;
    if(root->left or root->right)root->data = total;
}