水中的鱼

Implement a basic calculator to evaluate a simple expression string. The expression string contains only  non-negative  integers,  + ,  -...

Given two integers representing the numerator and denominator of a fraction, return the fraction in string format. If the fractional part...

Given a 2d grid map of  '1' s (land) and  '0' s (water), count the number of islands. An island is surrounded by water and ...

Implement a basic calculator to evaluate a simple expression string. The expression string may contain open  (  and closing parentheses  ...

Given an array of integers where 1 ≤ a[i] ≤   n   ( n   = size of array), some elements appear twice and others appear once. Find all the...

You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected hori...

Given an input string, reverse the string word by word. For example, Given s = " the sky is blue ", return " blue is sky...

Given an array of meeting time intervals consisting of start and end times  [[s1,e1],[s2,e2],...]  (s i  < e i ), find the minimum numbe...

According to the  Wikipedia's article : "The  Game of Life , also known simply as  Life , is a cellular automaton devised by the B...

Given a matrix of M x N elements (M rows, N columns), return all elements of the matrix in diagonal order as shown in the below image. Ex...

A frog is crossing a river. The river is divided into x units and at each unit there may or may not exist a stone. The frog can jump on a s...

Given a string representing arbitrarily nested ternary expressions, calculate the result of the expression. You can always assume that the ...

Given a binary tree, return the preorder traversal of its nodes' values. For example: Given binary tree {1,#,2,3} , 1 \ ...

Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space?   [Thoughts] 设定两个指针，一个每次走一步，一...

Given an integer  n , generate a square matrix filled with elements from 1 to  n 2  in spiral order. For example, Given  n  =  3 , You ...

Given a collection of intervals, merge all overlapping intervals. For example, Given  [1,3],[2,6],[8,10],[15,18] , return  [1,6],[8,10],...

Implement regular expression matching with support for  '.'  and  '*' . '.' Matches any single character. '*...

Given a string containing just the characters  '('  and  ')' , find the length of the longest valid (well-formed) parenthe...

Given an integer, print the closest number to it that is a palindrome - eg, the number "1224" would return "1221". [Th...

A message containing letters from  A-Z  is being encoded to numbers using the following mapping: 'A' -> 1 'B' -> 2 ...