LeetCode 1: Two Sum Solution
Master LeetCode problem 1 (Two Sum), a easy challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.
1. Two Sum
Problem Explanation
Explanation
To solve this problem efficiently, we can use a hashmap to store the difference between the target value and the current element in the array. As we iterate through the array, we check if the current element exists in the hashmap. If it does, we have found a pair of elements that add up to the target value. If not, we store the difference in the hashmap for future reference.
- Time complexity: O(n) - We iterate through the array once.
- Space complexity: O(n) - We store up to n elements in the hashmap.
Solution Code
import java.util.HashMap;
class Solution {
public int[] twoSum(int[] nums, int target) {
HashMap<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
int complement = target - nums[i];
if (map.containsKey(complement)) {
return new int[] { map.get(complement), i };
}
map.put(nums[i], i);
}
throw new IllegalArgumentException("No two sum solution");
}
}Try It Yourself
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The time complexity for LeetCode 1 (Two Sum) varies by solution. Check the detailed explanation section for specific complexities in Java, C++, and Python implementations.
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