LeetCode 1 Two Sum

LeetCode 1 Two Sum

Description

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].

解题思路

map，键是数字，值是数字的位置。

代码

class Solution {
public:
vector<int> twoSum(vector<int> &nums, int target) {
vector<int> ans;
unordered_map<int, int> map;
for (int i = 0, size = (int) nums.size(); i < size; ++i) {
map[nums[i]] = i + 1;
}
for (int i = 0, size = (int) nums.size(); i < size; ++i) {
int tmp = map[target - nums[i]];
if (tmp != 0 && tmp != i + 1) {
ans.push_back(i);
ans.push_back(tmp - 1);
break;
}
}
return ans;
}
};