1.Two Sum

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:
Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

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

public int[] twoSum(int[] nums, int target) {
    int[] result = new int[2];
    int[] ans = new int[2];
    int[] arr = Arrays.copyOf(nums, nums.length);
    Arrays.sort(arr);
    for(int i = 0, j = arr.length - 1; i <= j;) {
        int temp = arr[i] + arr[j];
        if(temp == target) {
            result[0] = arr[i];
            result[1] = arr[j];
            break;
        } else if(temp < target) {
            i++;
        } else {
            j--;
        }
    }
    int cnt = 0;
    for(int i = 0; i < nums.length; i++) {
        if(result[0] == nums[i] || result[1] == nums[i])
            ans[cnt++] = i;
    }
    return ans;

}