LeetCode 1、Two Sum

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].

https://leetcode.com/problems/two-sum/?tab=Description

Hash。

class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {

vector<int> result;
map<int, int> hash;

for (int i = 0; i < nums.size(); ++i) {
if (hash.count(nums[i]) != 0) {
result.push_back(hash[nums[i]]);
result.push_back(i);
break;
}
hash[target - nums[i]] = i;
}
return result;
}
};