Leetcodes Solution 1 Two Sum

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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].

思路1

用一個map來臨時存放沒有找到匹配的數

class Solution{public: vector<int> twoSum(vector<int>& nums, int target){ //key is the number and value is its index in the vector. unordered_map<int, int> hash; vector<int> result; for(int i = 0; i < nums.size(); i++){ int numberToFind = target - nums[i]; //if numberToFind is found in map, return them if(hash.find(numberToFind) != hash.end()){ result.push_back(hash[numberToFind]); result.push_back(i); return result; } //number was not found. Put it in the map hash[nums[i]] = i; } return result; }};

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