Category Archives: Stack and Queue

Reverse Nodes in k-Group

Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. If the number of nodes is not a multiple of k then left-out nodes in the end should remain as it is. You may … Continue reading

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Valid Parentheses

Given a string containing just the characters ‘(‘, ‘)’, ‘{‘, ‘}’, ‘[‘ and ‘]’, determine if the input string is valid. The brackets must close in the correct order, “()” and “()[]{}” are all valid but “(]” and “([)]” are not. C++: 01 class Solution { 02 public: 03     bool isValid(string s) { 04      … Continue reading

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Longest Valid Parentheses

Given a string containing just the characters ‘(‘ and ‘)’, find the length of the longest valid (well-formed) parentheses substring. For “(()”, the longest valid parentheses substring is “()”, which has length = 2. Another example is “)()())”, where the longest valid parentheses substring is “()()”, which … Continue reading

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Multiply Strings

Given two numbers represented as strings, return multiplication of the numbers as a string. Note: The numbers can be arbitrarily large and are non-negative. C++: 001 string shift(string s,int t) 002 { 003     if(s==“0”) 004         return s; 005  … Continue reading

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Rotate List

Given a list, rotate the list to the right by k places, where k is non-negative. For example: Given 1->2->3->4->5->NULL and k = 2, return 4->5->1->2->3->NULL. C++: 01 /** 02  * Definition for singly-linked list. 03  * struct ListNode { 04  *     int val; 05  *     ListNode … Continue reading

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Maximal Rectangle

Given a 2D binary matrix filled with 0’s and 1’s, find the largest rectangle containing all ones and return its area. C++: 01 class Solution { 02 public: 03     int maximalRectangle(vector<vector<char> > &matrix) { 04         // Start typing … Continue reading

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Largest Rectangle in Histogram

Given n non-negative integers representing the histogram’s bar height where the width of each bar is 1, find the area of largest rectangle in the histogram. Above is a histogram where width of each bar is 1, given height = [2,1,5,6,2,3]. C++: 01 class … Continue reading

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