随笔分类 - Leetcode+题
摘要：Given an array of integers, find two numbers such that they add up to a specific target number. The function twoSum should return indices of the two n
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摘要：Given an index k, return the k th row of the Pascal's triangle. For example, given k = 3,Return[1,3,3,1]. Note: Could you optimize your algorithm to u
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摘要：Given numRows, generate the first numRows of Pascal's triangle. For example, given numRows = 5,Return 题意：给定行数构建帕斯卡三角。 思路：注意行数和该行中列数的关系，还有每行中非首尾元素时，该元素
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摘要：Divide two integers without using multiplication, division and mod operator. 题意：两数相除不能用乘法、除、取余运算。 思路：直观的想法是相减，使用计算器p记下相减的次数n，这样时间复杂度为O(n)（n代表相减次数）。这是如
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摘要：Given a string containing only digits, restore it by returning all possible valid IP address combinations. For example:Given"25525511135", return["255
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摘要：Given a collection of numbers that might contain duplicates, return all possible unique permutations. For example,[1,1,2]have the following unique per
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摘要：Given a collection of numbers, return all possible permutations. For example,[1,2,3]have the following permutations:[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3
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摘要：Implement pow(x, n). 题意：计算x的次方 思路：这题的思路和sqrt的类似，向二分靠近。例如求4^5，我们可以这样求：res=4、4*4^4。就是将每次在res的基础上乘以x本身，换成，每次以x*=x的方式前行，这样时间复杂度为O(logn)，代码如下： 把x的n次方划分成两个x
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摘要：Implementint sqrt(int x). Compute and return the square root of x. 题意：求根号下x 的值 思路：使用二分搜索。先定义x平方根的取值区间，取值区间不同，在一些细节处理上也是不同的。这里去right为(x/2)+1，这是因为一个非负数x
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摘要：Write a function to find the longest common prefix string amongst an array of strings. 题意：找出所有字符串共同的最长前缀； 思路：因为是共同前缀，所以，求得第一个字符串和第二个字符的共同前缀以后，以这个前缀和后面
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摘要：Reverse digits of an integer. Example1: x = 123, return 321Example2: x = -123, return -321 click to show spoilers. Have you thought about this? Here a
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摘要：Given an array of integers, every element appears three times except for one. Find that single one. Note: Your algorithm should have a linear runtime
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摘要：Given an array of integers, every element appears twice except for one. Find that single one. Note: Your algorithm should have a linear runtime comple
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摘要：Sort a linked list using insertion sort. 题意：使用插入排序排链表。 思路：所谓的插入排序法，可以理解为，从原链表中取结点，每次都从新的链表的开头开始遍历比较，在新链表中找到不小于当前节点的位置，然后将当前节点插入进去，依次重复这种过程，时间复杂度为O(n^2
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摘要：Given a set of non-overlapping intervals, insert a new interval into the intervals (merge if necessary). You may assume that the intervals were initia
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摘要：Evaluate the value of an arithmetic expression in Reverse Polish Notation. Valid operators are+,-,*,/. Each operand may be an integer or another expre
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摘要：Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.
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摘要：Given a string containing just the characters'('and')', find the length of the longest valid (well-formed) parentheses substring. For"(()", the longes
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摘要：Given a string containing just the characters'(',')','{','}','['and']', determine if the input string is valid. The brackets must close in the correct
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摘要：Given a 2D binary matrix filled with 0's and 1's, find the largest rectangle containing all ones and return its area. 题意：求全由1组成的最大矩形面积。 思路：这题感觉是larges
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