[leetcode] Two Sum
2014-11-06 15:36
316 查看
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
(超时)暴力求解方法:
利用Hashmap,首先遍历数组,将numbers[index]=value, 存入hashmap<value,index>;然后遍历数组,在hashmap中寻找对应的值。
In addtion:
Map<Integer,Integer> map=new HashMap<Integer,Integer>(); //新建map
map.put(numbers[i],i) // put(key,value) 存入键值
map.get(numbers[i]); //get(key)取值
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
(超时)暴力求解方法:
public int[] twosum(int[]numbers, int target){ int[] result=new int[2]; int len=numbers.length; int sum; for(int i=0;i<len-1;i++){ for(int j=i+1;j<len;j++){ sum=numbers[i]+numbers[j]; if(sum==target){ result[0]=i+1; result[1]=j+1; } } } return result; }
利用Hashmap,首先遍历数组,将numbers[index]=value, 存入hashmap<value,index>;然后遍历数组,在hashmap中寻找对应的值。
public class Solution { public int[] twoSum(int[] numbers, int target) { int[] result=new int[2]; int len=numbers.length; Map<Integer, Integer> map = new HashMap<Integer, Integer>(); for(int i=0;i<len;i++){ map.put(numbers[i], i); } for(int one=0;one<len;one++){ Integer two=map.get(target-numbers[one]); if(two!=null && one<two){ result[0]=one+1; result[1]=two+1; } } return result; } }
In addtion:
Map<Integer,Integer> map=new HashMap<Integer,Integer>(); //新建map
map.put(numbers[i],i) // put(key,value) 存入键值
map.get(numbers[i]); //get(key)取值
相关文章推荐
- leetcode 虐我篇之(二) Two Sum
- LeetCode.Problem 1 Two Sum
- Leetcode-1:Two Sum
- leetcode-1 two sum
- LeetCode 第一题,Two Sum
- LeetCode Two Sum
- LeetCode----Two Sum
- LeetCode(1)Two Sum
- LeetCode: Two Sum
- LeetCode #1Two Sum
- LeetCode 01 Two Sum
- LeetCode: Two Sum
- LeetCode Two Sum
- LeetCode-1. Two Sum
- 1_Two Sum --LeetCode
- [leetcode] 1.two sum
- LeetCode_1_Two Sum
- [Leetcode]Two Sum
- [leetcode] 1. Two Sum
- [LeetCode]Two Sum 【Vector全局指针的使用】