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  1. #include <stdio.h> 
  2. #include <stdlib.h> 
  3. void swap(int* a, int* b) 
  4. { 
  5.     int temp; 
  6.     temp = *a; 
  7.     *a = *b; 
  8.     *b = temp; 
  9. } 
  10. int segregate(int arr[], int size) 
  11. { 
  12.     int j = 0, i; 
  13.     for (i = 0; i < size; i++) { 
  14.         if (arr[i] <= 0) { 
  15.             swap(&arr[i], &arr[j]); 
  16.             j++;  
  17.         } 
  18.     } 
  19.  
  20.     return j; 
  21. } 
  22.  
  23. int findMissingPositive(int arr[], int size) 
  24. { 
  25.     int i; 
  26.    for (i = 0; i < size; i++) { 
  27.         if (abs(arr[i]) - 1 < size && arr[abs(arr[i]) - 1] > 0) 
  28.             arr[abs(arr[i]) - 1] = -arr[abs(arr[i]) - 1]; 
  29.     } 
  30.  
  31.         for (i = 0; i < size; i++) 
  32.         if (arr[i] > 0) 
  33.             return i + 1; 
  34.      return size + 1; 
  35. } 
  36. int findMissing(int arr[], int size) 
  37. { 
  38.      int shift = segregate(arr, size);
  39.     return findMissingPositive(arr + shift, size - shift); 
  40. } 
  41.  
  42. int main() 
  43. { 
  44.     int arr[10],n; 
  45.     scanf("%d",&n);
  46.     for(int i=0;i<n;i++)
  47.     scanf("%d",&arr[i]);
  48.     int missing = findMissing(arr, n); 
  49.     printf("The missing number is %d ", missing);
  50.     return 0; 
  51. } 
  52.  
  53.  
Success #stdin #stdout 0s 4236KB
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The missing number is 2
https://ideone.com/wXQDpy
language:
C (gcc 8.3)
created:
4 years ago
visibility:
public

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