leetcode/1-two-sum/1-two-sum.cs

public class Solution {
    public int[] TwoSum(int[] nums, int target) {
        for (int i = 0; i < nums.Length; i++) {
            for (int j = i + 1; j < nums.Length; j++) {
                if (nums[i] + nums[j] == target) {
                    return new int[] {i , j};
                }
            }
        }
        return null;
    }
}