【LeetCode】- Two Sum(两数相加)
来源:互联网 发布:淘宝店天天特价 编辑:程序博客网 时间:2024/06/10 16:16
[ 问题: ]
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 numbers such that they add up to the target, where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.
You may assume that each input would have exactly one solution.
Input: numbers={2, 7, 11, 15}, target=9
Output: index1=1, index2=2
题意: 给定一个整数, 从里面找出两个数, 其和等于一个指定的整数. 程序返回这两个数在数组中的位置( 数组下标从1开始 ) , 且位置小的在前面.
[ 常规: ]
下面的解法时间复杂度为O(n * m), 也是很多人第一反应就能得出的解法, 但是非常的遗憾, 这个解法无法AC.
Status: Time Limit Exceeded
public class Solution {public int[] twoSum(int[] numbers, int target) {int[] result = new int[2];for (int i = 0; i < numbers.length; i++) {int temp = target - numbers[i];for (int j = i + 1; j < numbers.length; j++) {if (numbers[j] == temp) {result[0] = i + 1;result[1] = j + 1;return result;}}}return result;}public static void main(String[] args) {int[] numbers = { 2, 7, 11, 15 };int target = 9;int[] result = new Solution().twoSum(numbers, target);for (int i = 0; i < result.length; i++) {System.out.println(result[i]);}}}
[ 正解: ]
下面的巧妙的利用map帮我们记住了值和索引, 对每一个数边查边存, 时间复杂度为O(n)
public class Solution {public int[] twoSum(int[] numbers, int target) {HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();int[] result = new int[2];for (int i = 0; i < numbers.length; i++) {if (map.get(target - numbers[i]) != null) {result[0] = map.get(target - numbers[i]) + 1;result[1] = i + 1;break;} else {map.put(numbers[i], i);}}return result;}public static void main(String[] args) {int[] numbers = { 2, 7, 11, 15 };int target = 17;int[] result = new Solution().twoSum(numbers, target);for (int i = 0; i < result.length; i++) {System.out.println(result[i]);}}}
5 0
- 【LeetCode】- Two Sum(两数相加)
- [LeetCode]371.Sum of Two Integers两数相加
- LeetCode-Two Sum(两数之和)
- LeetCode OJ 之 Add Two Numbers (”两数“相加)
- LeetCode 2. Add Two Numbers(两数相加)
- 链表:链表两数相加( LeetCode 2. Add Two Numbers(两数相加))
- leetcode——Two Sum 两数之和(AC)
- LeetCode 1. Two Sum(两数之和)
- LeetCode Two Sum 两数之和
- leetcode 1 Two Sum 两数之和
- [leetcode, python] Two Sum 两数之和等于某数
- Two Sum(两数之和)
- 1、Two Sum(两数之和)
- leetcode 1. Two Sum两数和(HashMap)
- leetcode 1: 找出两个数相加等于给定数 two sum
- LeetCode 167. Two Sum II - Input array is sorted(两数和)
- LeetCode 170. Two Sum III - Data structure design(两数和)
- Two Sum--两数之和
- sql server2012附加数据库问题
- 数据结构(C)---汉诺塔随记
- DAVINCI DM3730开发攻略——U-BOOT-2010.06的移植
- leetcode第一刷_Integer to Roman
- gradle编译自定义注解(annotation)的未解决问题
- 【LeetCode】- Two Sum(两数相加)
- eclipse启动优化
- PHP出现mktime()date()时间timezone警告的解决方法,尤其是phpExcelReader会出现这个警告
- 实战Linux Bluetooth编程(三) HCI层编程
- 关于jdbc 源码解析 DriverManager 和 ServiceLoader
- [GitHub][2014-05-14 22:00:17]65ca
- go语言:flag的使用
- 自定义计算表达式的函数
- 第七讲 常用的Web服务器控件(一)