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].
Solution:
Use a map to save all positions of nums, try to find target-nums[i].
class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
map<int,int> pos;
for(int i=0;i<nums.size();i++){
if(pos.find(target-nums[i]) != pos.end()){
return vector<int>{pos[target-nums[i]], i};
}
pos[nums[i]] = i;
}
return vector<int>();
}
};