Question

How to get the first missing smallest positive integer in an unsorted integer array with C#

Answer 1

using System;
using System.Collections.Generic;

class Program
{
    static int FindSmallestMissingNumber(int[] arr) {
        HashSet<int> numSet = new HashSet<int>(arr);
        
        int index = 1;
        while (true) {
            if (!numSet.Contains(index)) {
                return index;
            }
            index++;
        }
        
        return -999;
    }

    static void Main()
    {
        int[] arr = { 3, 4, -1, 1 };
        
        Console.WriteLine(FindSmallestMissingNumber(arr));
    }
}



/*
run:

2

*/

 

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