zoukankan      html  css  js  c++  java
  • [leetCode]100.相同的树

    解法一 递归

    从根结点开始,首先判断两棵树根节点是否为null,再判断是否相等,然后再对左子树与右子树进行相同的操作。

    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */
    class Solution {
        public boolean isSameTree(TreeNode p, TreeNode q) {
            if(p==null && q == null) return true;
            if(p == null | q ==null) return false;
            if(p.val != q.val) return false;
            else return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
        }
    }
    

    解法二 迭代

    使用两个双端队列,从根节点开始每次迭代弹出两个对应的节点,
    用check方法判断两个节点p、q是否满足:

    • p、q不为null
    • p.val = q.val

    如果满足则继续压入子节点

    /**
     * Definition for a binary tree node.
     * public class TreeNode {
     *     int val;
     *     TreeNode left;
     *     TreeNode right;
     *     TreeNode(int x) { val = x; }
     * }
     */
    class Solution {
        public boolean isSameTree(TreeNode p, TreeNode q) {
            if(p == null && q == null) return true;
            if(!check(p,q)) return false; 
    
            ArrayDeque<TreeNode> deqP = new ArrayDeque<>();
            ArrayDeque<TreeNode> deqQ = new ArrayDeque<>();
            deqP.addLast(p);
            deqQ.addLast(q);
    
            while(!deqP.isEmpty()){
                p = deqP.removeFirst();
                q = deqQ.removeFirst();
                if(!check(p,q)) return false;
                if(p!=null){
                    if(!check(p.left,q.left)) return false;
                    if(p.left != null){//check返回true有两种情况,确保p.left 与 q.left 不为null
                        deqP.addLast(p.left);
                        deqQ.addLast(q.left);
                    }
                    if(!check(p.right,q.right)) return false;
                    if(p.right != null){
                        deqP.addLast(p.right);
                        deqQ.addLast(q.right);
                    }
                }
            }
            return true;
        }
        
        //检查pq节点是否相等
        public boolean check(TreeNode p, TreeNode q){
            if(q == null && p == null) return true;
            if(q == null || p == null) return false;
            if(p.val != q.val) return false;
            return true;
        }
    }
    
  • 相关阅读:
    poj1703--Find them, Catch them
    poj2828--Buy Tickets
    POJ 2594 Treasure Exploration(Floyd+最小路径覆盖)
    HDU
    二分图的一些性质
    HDU
    POJ 1659 Frogs' Neighborhood (Havel定理构造图)
    HDU
    HDU
    2018 Multi-University Training Contest 1
  • 原文地址:https://www.cnblogs.com/PythonFCG/p/13860015.html
Copyright © 2011-2022 走看看