1. 38. Count and Say 就是对于前一个数,找出相同元素的个数,把个数和该元素存到新的string里.数量+字符 class Solution { public String countAndSay(int n) { if( n == 1) return "1"; StringBuffer sb = new StringBuffer(); String str = countAndSay(n - 1); int count = 0; char c = '0'; for(…

LeetCode第28题 Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Example 1: Input: haystack = "hello", needle = "ll" Output: 2 Example 2: Input: haystack = "aaaaa", needle…

# -*- coding: utf8 -*-'''__author__ = 'dabay.wang@gmail.com' 28: Implement strStr()https://oj.leetcode.com/problems/implement-strstr/ Implement strStr().Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of h…

Given an unsorted array, find the maximum difference between the successive elements in its sorted form. Try to solve it in linear time/space. Return 0 if the array contains less than 2 elements. You may assume all elements in the array are non-negat…

原题地址: 344 Reverse String: https://leetcode.com/problems/reverse-string/description/ 541 Reverse String II: https://leetcode.com/problems/reverse-string-ii/description/ 题目&&解法: 1.Reverse String: Write a function that takes a string as input and ret…

You need to construct a string consists of parenthesis and integers from a binary tree with the preorder traversing way. The null node needs to be represented by empty parenthesis pair "()". And you need to omit all the empty parenthesis pairs t…

Special binary strings are binary strings with the following two properties: The number of 0's is equal to the number of 1's. Every prefix of the binary string has at least as many 1's as 0's. Given a special string S, a move consists of choosing two…

Given a string containing only three types of characters: '(', ')' and '*', write a function to check whether this string is valid. We define the validity of a string by these rules: Any left parenthesis '(' must have a corresponding right parenthesi…

Design and implement a data structure for a compressed string iterator. It should support the following operations: next and hasNext. The given compressed string will be in the form of each letter followed by a positive integer representing the numbe…

Given two strings s1 and s2, write a function to return true if s2 contains the permutation of s1. In other words, one of the first string's permutations is the substring of the second string. Example 1: Input:s1 = "ab" s2 = "eidbaooo"…