1.Two Sum

博主忙毕业的事情，一个半月木有刷题，感觉手都生了....

今天开始闭关修炼～～

先拿道简单的题练练手

Two Sum（熟悉吧熟悉吧）

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

这次用hashmap来解决

key—nums的值；

vaule－nums的indice

复杂度O(n)

package leetcode2;

import java.util.HashMap;

public class sum_two_hashmap {
	 public static int[] twoSum(int[] nums, int target) {
		 HashMap<Integer,Integer> map=new  HashMap<Integer,Integer>();
		 int[] res= new int[2];
		 int length=nums.length;
		 for(int i=0;i<length;i++){
			 if(map.containsKey(target-nums[i])){
				 res[0]=map.get(target-nums[i])+1;
				 res[1]=i+1;
				 break;
			 }else{
				 map.put(nums[i],i);
				 }
		 }
		 return res;
	 }
}

1.Two Sum

原文：http://www.cnblogs.com/joannacode/p/4539762.html