[1] Two Sum
https://leetcode.com/problems/two-sum/description/
- algorithms
- Easy (46.37%)
- Likes: 19171
- Dislikes: 682
- Total Accepted: 3.8M
- Total Submissions: 8.3M
- Testcase Example: ‘[2,7,11,15]\n9’
Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
You can return the answer in any order.
Example 1:
Input: nums = [2,7,11,15], target = 9 Output: [0,1] Output: Because nums[0] + nums[1] == 9, we return [0, 1].
Example 2:
Input: nums = [3,2,4], target = 6 Output: [1,2]
Example 3:
Input: nums = [3,3], target = 6 Output: [0,1]
Constraints:
2 <= nums.length <= 103-109 <= nums[i] <= 109-109 <= target <= 109- Only one valid answer exists.
Approach 1: Brute Force
Loop through each element x and find if there is another value that equals to target - x
class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
vector<int> answer;
int i, j;
for(i = 0; i< nums.size() - 1; i++){
for(j = i + 1; j < nums.size(); j++){
int diff = target - nums[j];
if(nums[i] == diff){
answer.push_back(i);
answer.push_back(j);
}
}
}
return answer;
}
};
Complexity Analysis
- Time Complexity: $O(n^2)$
- Space Complexity: $O(1)$
