Question

How to find the smallest missing number from unsorted array in C

Answer 1

#include <stdio.h>
#include <stdlib.h>
 
int compare(const void * a, const void * b) {
    return ( *(int*)a - *(int*)b );
}

int findSmallestMissingNumber(int arr[], int size) {
    int min = arr[0];
     
    for (int i = 1; i < size; i++) {
        if (arr[i] > min + 1) {
            return min + 1;
        } else {
            min = arr[i];
        }
    }
     
    return -1;
}
 
int main()
{
    int arr[] = {18, 19, 20, 27, 33, 36, 40, 42};
    int size = sizeof(arr)/sizeof(arr[0]);
 
    qsort(arr, size, sizeof(int), compare);
   
    printf("%i", findSmallestMissingNumber(arr, size));
      
    return 0;
}
 
 
 
 
/*
run:
 
21
     
*/

 

 

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