leetcode-1-Two Sum

难度:

描述：

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, and you may not use the same element twice.

Example：

Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

我的解答

class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
int size = nums.size();
vector<int> temp;
for(int i = 0; i < size;i++)
for(int j=i+1;j < size;j++)
{
if(nums[i]+nums[j]==target)
{
temp.push_back(i);
temp.push_back(j);
}
}
return temp;
}
};

更好的解答

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