Given an unsorted integer array, find the smallest missing positive integer.
Example 1:
Input: [1,2,0] Output: 3Example 2:
Input: [3,4,-1,1] Output: 2Example 3:
Input: [7,8,9,11,12] Output: 1Note:
- Your algorithm should run in O(n) time and uses constant extra space.
使用O(n)的时间复杂度和O(1)的空间在无序数组中查找第一个缺失的正数。
Given two non-negative integers
num1andnum2represented as strings, return the product ofnum1andnum2, also represented as a string.Example 1:
Input: num1 = “2”, num2 = “3” Output: “6”
Example 2:
Input: num1 = “123”, num2 = “456” Output: “56088”
将两个字符串表示的数字相乘（大数相乘）。
Given a collection of candidate numbers (
candidates) and a target number (target), find all unique combinations in candidates where thecandidatenumbers sums totarget.Each number in
candidatesmay only be used once in the combination.Note:
All numbers (including
target) will be positive integers. The solution set must not contain duplicate combinations.
Given a set of candidate numbers (
candidates) (without duplicates) and a target number (target), find all unique combinations incandidateswhere the candidate numbers sums totarget.The same repeated number may be chosen from candidates unlimited number of times.
Note:
- All numbers (including
target) will be positive integers.- The solution set must not contain duplicate combinations.
Determine if a 9x9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules:
- Each row must contain the digits
1-9without repetition.- Each column must contain the digits
1-9without repetition.- Each of the 9
3x3sub-boxes of the grid must contain the digits1-9without repetition.
A partially filled sudoku which is valid.
The Sudoku board could be partially filled, where empty cells are filled with the character
'.'.
验证数独
Search in Rotated Sorted Array
Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.
(i.e.,
[0,1,2,4,5,6,7]might become[4,5,6,7,0,1,2]).You are given a target value to search. If found in the array return its index, otherwise return
-1.You may assume no duplicate exists in the array.
Your algorithm’s runtime complexity must be in the order of
O(log n).
Given a string containing just the characters
'('and')', find the length of the longest valid (well-formed) parentheses substring. Example 1:Input: "(()" Output: 2 Explanation: The longest valid parentheses substring is "()"
输出最长的左右括号匹配的子串长度
Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers.
If such arrangement is not possible, it must rearrange it as the lowest possible order (ie, sorted in ascending order).
The replacement must be in-place and use only constant extra memory.
Here are some examples. Inputs are in the left-hand column and its corresponding outputs are in the right-hand column.
1,2,3→1,3,23,2,1→1,2,31,1,5→1,5,1
实现字典序排列的 nextPermutation 方法，假如已经是最大排列，则输出最小排列。
