Two Sum
Find two numbers that add up to a target and learn how to recognize when a hash map can turn repeated searching into constant-time lookup.
Problem
Two Sum
The Problem
You are given an array of integers nums and an integer target.
Find two different elements in the array whose values add up to target, and return their indices.
You may assume that exactly one valid answer exists.
Example 1
Input:
4 9
2 7 11 15
Output:
0 1
Because:
2 + 7 = 9
Example 2
Input:
3 6
3 2 4
Output:
1 2
Because:
2 + 4 = 6
Example 3
Input:
2 6
3 3
Output:
0 1
Before You Look at the Hints
Try this problem yourself first.
Don't immediately search for the optimal solution.
Start with the simplest approach you can think of.
Write the code. Run it.
Then ask yourself:
What makes my solution slow?
That question is more important than getting the answer quickly.
Examples
Input
4 9 2 7 11 15
Output
0 1
Input
3 6 3 2 4
Output
1 2
Input
2 6 3 3
Output
0 1
YOUR SOLUTION
Try it yourself
Run against the examples first. Submit when you're confident.
Ready to run
TEST CASES
Check your thinking
Input
4 9 2 7 11 15
Expected Output
0 1
Input
3 6 3 2 4
Expected Output
1 2
Input
2 6 3 3
Expected Output
0 1
Elvoret Approach
Stuck? Use a hint.
Try the problem yourself first. If you get stuck, reveal the hints one at a time. After all three hints, you can reveal the complete answer.