Two Sum

Given an array of integers, find two numbers such that they add up to a specific target number.

• Time: O(n)
• Space: O(1)

public int[] twoSum(int[] nums, int target) {
    int[] ret = new int[2];
    Map<Integer, Integer> map = new HashMap<>();
    for (int i = 0; i < nums.length; i++) {
        if (map.containsKey(target - nums[i])) {
            ret[0] = map.get(target - nums[i]);
            ret[1] = i;
            break;
        }
        map.put(nums[i], i);
    }
    return ret;
}