max-sum-root-to-leaf.js

/*
You are given a binary tree. Implement the method maxSum which returns the maximal sum of a route from root to leaf. For example, given the following tree:

    17
   /  \
  3   -10
 /    /  \
2    16   1
         /
        13

The method should return 23, since [17,-10,16] is the route from root to leaf with the maximal sum.

The class TreeNode is available for you:

var TreeNode = function(value, left, right) {
  this.value = value;
  this.left = left;
  this.right = right;
};

*/

function maxSum(root) {

    if(!root) return 0
    
    const leftSum = maxSum(root.left)
    const rightSum = maxSum(root.right)
    
    return root.value + Math.max(leftSum, rightSum)
    
}

/*
Just understand how post order dfs works and you'll understand how the sum works
*/