LeetCode第20题Given a string containing just the characters ‘(‘, ‘)‘, ‘{‘, ‘}‘, ‘[‘ and ‘]‘, determine if the input string is valid.An input string is valid if:Open brackets must be closed by the same type of brackets.Open brackets must be closed in the correct order.Note that an empty string is also considered valid.Example 1:Input: "()"
Output: trueExample 2:Input: "()[]{}"
Output: t...
N皇后问题源于著名的八皇后问题：在8×8格的国际象棋上摆放八个皇后，使其不能互相攻击，即任意两个皇后都不能处于同一行、同一列或同一斜线上，问有多少种摆法！将8x8扩展为NxN即为N皇后问题，要解决此问题，最简单的方法就是暴力枚举，此时的时间复杂度为N^2，回溯算法与简单暴力枚举类似，不同点在于当判定某种状态不符合答案时，便不再继续枚举此状态的后续状态，而是回溯到该状态之前，继续遍历其他的可能值。 1 #include <ios...
【034-Search for a Range（搜索一个范围）】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】原题 Given a sorted array of integers, find the starting and ending position of a given target value. Your algorithm’s runtime complexity must be in the order of O(log n). If the target is not found in the array, return [-1, -1]. For example, Given [5, 7, 7, 8, 8, 10] and target value 8, return [3, ...
【225-Implement Stack using Queues（用队列实现栈操作）】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】代码下载【https://github.com/Wang-Jun-Chao】原题 Implement the following operations of a stack using queues. push(x) – Push element x onto stack. pop() – Removes the element on top of the stack. top() – Get the top element. empty() – Return whether the stack is empty. Notes: You mus...
【101-Symmetric Tree（对称树）】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】原题 Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). For example, this binary tree is symmetric: 1/ 2 2/ \ / 3 4 4 3 But the following is not: 1/ 2 2\ 3 3 Note: Bonus points if you could solve it both recursively and iteratively.题目大意...
【070-Set Matrix Zeroes（矩阵置零）】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】原题 Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place. 题目大意 给定一个m*n的矩阵，如果某个位置是0。将对应的行和列设置为0。 解题思路 先对矩阵进行扫描，标记要进行置0的行和列，对要进行置0的行在第0列上进行标记，对置0的列在第0行上进行标标记。同时还要两变量记录...
LeetCode剑指offer二叉树系列07 重建二叉树题目输入某二叉树的前序遍历和中序遍历的结果，请重建该二叉树。假设输入的前序遍历和中序遍历的结果中都不含重复的数字。
例如，给出
前序遍历 preorder = [3,9,20,15,7]
中序遍历 inorder = [9,3,15,20,7]
返回如下的二叉树：3/ 9 20/ 15 7来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/zhong-jian-er-cha-shu-lcof
著作权归领扣网络所有。商业转载请联系官...
题目：填充每个节点的下一个右侧节点指针：给定一个完美二叉树，其所有叶子节点都在同一层，每个父节点都有两个子节点。给定一个完美二叉树，其所有叶子节点都在同一层，每个父节点都有两个子节点。二叉树定义如下：struct Node { int val; Node *left; Node *right; Node *next;}填充它的每个 next 指针，让这个指针指向其下一个右侧节点。如果找不到下一个右侧节点，则将 next 指针设置为 NULL。初始状态下，所有 next 指针都...
Search in Rotated Sorted Array I && IILeetcode对有序数组进行二分查找（下面仅以非递减数组为例）：int binarySort(int A[],int lo,int hi,int target){while(lo <= hi){int mid = lo +(hi - lo)/2;if(A[mid]== target)return mid;if(A[mid]< target) lo = mid +1;else hi = mid -1;}}对有序的旋转数组进行二分查找：eg. [7, 8, 9, 3, 4, 5, 6]在数组中有且仅有一个 断点 （数字由大变小）。还是通过折半...
【057-Insert Interval（插入区间）】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】原题 Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initially sorted according to their start times. Example 1: Given intervals [1,3],[6,9], insert and merge [2,5] in as [1,5],[6,9]. Example 2: Given [1,2],[3,5]...
#include<math.h>
class Solution {
private:vector<string> solution;vector< vector <int>> result;vector<int> columns;
public:bool check(int row, int col){for(int r=0; r<row; r++)if(columns[r] == col || (row-r) == abs(columns[r]-col))returnfalse;returntrue;}void backtracking(int n, int row){if(row == n){result.push_back(columns);return;} for(int col=0; col<n; col++){columns.push_back(col);if(check(r...
本来想写完递归再写这个专栏的，但是老师给了一个贪心的题目，没办法只能开一个板块了简介在对问题求解时，总是做出在当前看来是最好的选择。也就是说，不从整体最优上加以考虑，算法得到的是在某种意义上的局部最优解。与这个局部最优解相对应的全局最优解会在动态规划里面展现出来。例题先来一道经典的贪心热热手，跳跃游戏就算是一个比较经典的贪心题思路一开始看到这个题目不知不觉开始用动态规划在写了 (°ー°〃)仔细一看返回值...
1、题目 – Sqrt(x)Implement int sqrt(int x).Compute and return the square root of x.题目意思很简单，就是求出x的平方根。分析：一看这题目，感觉很简单，很容易想到的是二分法，我最开始的解法是从1、2、4、8 … 2 * n，计算出n < x < 2n，然后再在 n 和 2n间，用二分法，找到平方根结果。这种方法比较麻烦的一点是，乘积是有可能越界的，要处理乘积越界的情况，代码可读性不强。class Solution {
public:int sqrt(int x) {i...
【024-Swap Nodes in Pairs（成对交换单链表的结点）】【LeetCode-面试算法经典-Java实现】【所有题目目录索引】原题 Given a linked list, swap every two adjacent nodes and return its head. For example, Given 1->2->3->4, you should return the list as 2->1->4->3. Your algorithm should use only constant space. You may not modify the values in the list, only nodes itself can be changed. 题目大意 给定一...
Given a binary tree, find all leaves and then remove those leaves. Then repeat the previous steps until the tree is empty. Example:
Given binary tree 1/ 2 3/ \ 4 5
Returns [4, 5, 3], [2], [1]. Explanation:
1. Remove the leaves [4, 5, 3] from the tree1/ 2
2. Remove the leaf [2] from the tree 1
3. Remove the leaf [1] from the tree [...
