LeetCode[1] Two Sum (java实现)

Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution.
Example
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

根据提交情况分析得出，如果target=14，则应该返回[1,1].

最笨的方法，提交通过
public class Solution {
public int[] twoSum(int[] nums, int target) {
for(int i=0;i<nums.length;i++){
for(int j=i+1;j<nums.length;j++){
if((nums[i]+nums[j])==target){
return new int[]{i,j};
}
}
}
for(int i=0;i<nums.length;i++){
if(2*nums[i]==target){
return new int[]{i,i};
}
}
throw new IllegalArgumentException("no two sum solution");
}
}

系统提供的解法
public int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
int complement = target - nums[i];
if (map.containsKey(complement)) {
return new int[] { map.get(complement), i };
}
map.put(nums[i], i);
}
throw new IllegalArgumentException("No two sum solution");
}