题解 | #二叉树的后序遍历#

/*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)
 *     }
 * }
 */
/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param root TreeNode类 
 * @return int整型一维数组
 */
export function postorderTraversal(root: TreeNode): number[] {
    // write code here
    const result:number[] = []
    function tranversal(root){
        if(!root)return;
        tranversal(root.left);
        tranversal(root.right);
        result.push(root.val);
    }
    tranversal(root);
    return result;
}