124. 二叉树中的最大路径和

题解

/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     val: number
 *     left: TreeNode | null
 *     right: TreeNode | null
 *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
 *         this.val = (val===undefined ? 0 : val)
 *         this.left = (left===undefined ? null : left)
 *         this.right = (right===undefined ? null : right)
 *     }
 * }
 */
function maxPathSum(root: TreeNode | null): number {
    let min = Number.MIN_SAFE_INTEGER;
    function deepLoop(node: TreeNode | null) {
        if (!node) return 0;
        let left = Math.max(0, deepLoop(node.left));
        let right = Math.max(0, deepLoop(node.right));
        min = Math.max(min, left + right + node.val);
        return Math.max(left, right) + node.val;
    }
    deepLoop(root);
    return min;
};