# Two Sum Leetcode Solution

In this post, we are going to solve the Two Sum Leetcode Solution problem of Leetcode. This Leetcode problem is done in many programming languages like C++, Java, and Python.

## Problem

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]
Explanation: Because nums + nums == 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 <= 104
• -109 <= nums[i] <= 109
• -109 <= target <= 109
• Only one valid answer exists.

Now, let’s see the leetcode solution of Two Sum Leetcode Solution.

### Two Sum Leetcode Solutionin Python

This is an O(N) complexity solution.

```class Solution:
def twoSum(self, nums: List[int], target: int) -> List[int]:
numToIndex = {}
for i, num in enumerate(nums):
if target - num in numToIndex:
return numToIndex[target - num], i
numToIndex[num] = i```

### Two Sum Leetcode Solutionin CPP

This is an O(N) complexity solution.

```class Solution {
public:
vector<int> twoSum(vector<int>& nums, int target) {
unordered_map<int, int> numToIndex;
for (int i = 0; i < nums.size(); ++i) {
if (numToIndex.count(target - nums[i]))
return {numToIndex[target - nums[i]], i};
numToIndex[nums[i]] = i;
}
throw;
}
};
```

### Two Sum Leetcode Solutionin Java

This is an O(N) complexity solution.

```class Solution {
public int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> numToIndex = new HashMap<>();
for (int i = 0; i < nums.length; ++i) {
if (numToIndex.containsKey(target - nums[i]))
return new int[] {numToIndex.get(target - nums[i]), i};
numToIndex.put(nums[i], i);
}
throw new IllegalArgumentException();
}
}```

Note: This problem  Two Sum is generated by Leetcode but the solution is provided by Chase2learn This tutorial is only for Educational and Learning purposes.

Next: Add Two Numbers Leetcode Solution

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