Ryan’s leetcode Blog

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only  distinct  numbers from the original list. For exa...

Follow up for "Unique Paths": Now consider if some obstacles are added to the grids. How many unique paths would there be? An...

Follow up for N-Queens problem. Now, instead outputting board configurations, return the total number of distinct solutions. 与 N-Quee...

Given a string  s  and a dictionary of words  dict , add spaces in  s  to construct a sentence where each word is a valid dictionary word. ...

Given an array of words and a length  L , format the text such that each line has exactly  L  characters and is fully (left and right) just...

Given a 2D board containing  'X'  and  'O' , capture all regions surrounded by  'X' . A region is captured by fli...

Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell,...

Given a  m  x  n  matrix, if an element is 0, set its entire row and column to 0. Do it in place. "这是一个矩阵操作的题目，目标很明确，就是如果矩阵如果有元素为0，就把...

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 matrix of  m  x  n  elements ( m  rows,  n  columns), return all elements of the matrix in spiral order. For example, Given the ...

Write a program to solve a Sudoku puzzle by filling the empty cells. Empty cells are indicated by the character  '.' . You may ...

Determine if a Sudoku is valid, according to:  Sudoku Puzzles - The Rules . The Sudoku board could be partially filled, where empty cells...

Given an unsorted integer array, find the first missing positive integer. For example, Given  [1,2,0]  return  3 , and  [3,4,-1,1]  ret...

Given an index  k , return the  k th  row of the Pascal's triangle. For example, given  k  = 3, Return  [1,3,3,1] . 与Pascal's ...

Given  numRows , generate the first  numRows  of Pascal's triangle. For example, given  numRows  = 5, Return [ [1], [1,1],...

You are given an  n  x  n  2D matrix representing an image. Rotate the image by 90 degrees (clockwise). Follow up: Could you do this i...

Implement next permutation, which rearranges numbers into the lexicographically next greater permutation of numbers. If such arrangement ...

Given an array and a value, remove all instances of that value in place and return the new length. The order of elements can be changed. ...

Given  n  non-negative integers  a 1 ,  a 2 , ...,  a n , where each represents a point at coordinate ( i ,  a i ).  n  vertical lines are ...

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