剑指offer刷题

# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
class Solution:
    # 返回ListNode
    def ReverseList(self, pHead):
        # write code here
        if pHead is None:
            return pHead
        last = None  #指向上一个节点
        while pHead:
            # 先用tmp保存pHead的下一个节点的信息，
            # 保证单链表不会因为失去pHead节点的next而就此断裂
            tmp = pHead.next
            # 保存完next，就可以让pHead的next指向last了
            pHead.next = last
            # 让last，pHead依次向后移动一个节点，继续下一次的指针反转
            last = pHead
            pHead = tmp
        return last

# -*- coding:utf-8 -*-
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None
 
class Solution:
    # 返回合并后列表
    def Merge(self, pHead1, pHead2):
        # write code here
        mergeHead = ListNode(90)
        # 这里是把头指针给了p
        p = mergeHead
        while pHead1 and pHead2:
            if pHead1.val >= pHead2.val:
                mergeHead.next = pHead2
                pHead2 = pHead2.next
            else:
                mergeHead.next = pHead1
                pHead1 = pHead1.next
                  
            mergeHead = mergeHead.next
        # 看看1和2哪个还没走完的
        if pHead1:
            mergeHead.next = pHead1
        elif pHead2:
            mergeHead.next = pHead2
        return p.next
                 

链接：https://www.nowcoder.com/questionTerminal/6e196c44c7004d15b1610b9afca8bd88
来源：牛客网

public class Solution {
    public static boolean HasSubtree(TreeNode root1, TreeNode root2) {
        boolean result = false;
        //当Tree1和Tree2都不为零的时候，才进行比较。否则直接返回false
        if (root2 != null && root1 != null) {
            //如果找到了对应Tree2的根节点的点
            if(root1.val == root2.val){
                //以这个根节点为为起点判断是否包含Tree2
                result = doesTree1HaveTree2(root1,root2);
            }
            //如果找不到，那么就再去root的左儿子当作起点，去判断时候包含Tree2
            if (!result) {
                result = HasSubtree(root1.left,root2);
            }
             
            //如果还找不到，那么就再去root的右儿子当作起点，去判断时候包含Tree2
            if (!result) {
                result = HasSubtree(root1.right,root2);
               }
            }
            //返回结果
        return result;
    }
 
    public static boolean doesTree1HaveTree2(TreeNode node1, TreeNode node2) {
        //如果Tree2已经遍历完了都能对应的上，返回true
        if (node2 == null) {
            return true;
        }
        //如果Tree2还没有遍历完，Tree1却遍历完了。返回false
        if (node1 == null) {
            return false;
        }
        //如果其中有一个点没有对应上，返回false
        if (node1.val != node2.val) {  
                return false;
        }
         
        //如果根节点对应的上，那么就分别去子节点里面匹配
        return doesTree1HaveTree2(node1.left,node2.left) && doesTree1HaveTree2(node1.right,node2.right);
    }

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    # 返回镜像树的根节点
    def Mirror(self, root):
        # write code here
        if root!=None:
            root.left,root.right=root.right,root.left
            self.Mirror(root.left)
            self.Mirror(root.right)

# -*- coding:utf-8 -*-
class Solution:
    def __init__(self):
        # 定义两个栈，其中一个是装小点的
        self.stack = []
        self.min_stack = []
    def push(self, node):
        # write code here
        self.stack.append(node)
        if(not self.min_stack or node <= self.min_stack[-1]):
            self.min_stack.append(node)
    def pop(self):
        # write code here
        if(self.stack[-1] == self.min_stack[-1]):
            self.min_stack.pop()
        return self.stack.pop()
    def top(self):
        # write code here
        return self.stack[-1]
    def min(self):
        # write code here
        return self.min_stack[-1]