Arrays & Hashing
Two sum
Given an array of integers nums and an integer target, return the indices i and j such that nums[i] + nums[j] == target and i != j.
- You may assume that every input has exactly one valid pair of indices that satisfy the condition.
- Return the answer with the smaller index first.
Examples:
Example 1:
- Input:
nums = [3, 4, 5, 6],target = 7 - Output:
[0, 1] - Explanation:
nums[0] + nums[1] == 7, so the output is[0, 1].
Example 2:
- Input:
nums = [4, 5, 6],target = 10 - Output:
[0, 2]
Example 3:
- Input:
nums = [5, 5],target = 10 - Output:
[0, 1]
Constraints:
2 <= nums.length <= 1000-10^7 <= nums[i] <= 10^7-10^7 <= target <= 10^7
public int[] twoSum(int[] nums, int target) {
HashMap<Integer, Integer> prevMap = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
int num = nums[i];
int diff = target - num;
if (prevMap.containsKey(diff)) {
return new int[] { prevMap.get(diff), i };
}
prevMap.put(num, i);
}
return new int[] {};
}
