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  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. int binary_search(int a[], int n, int x){
  5.     int left = 0;           
  6.     int right = n - 1;     
  7.  
  8.     while (left <= right) {
  9.         int mid = (left + right) / 2; 
  10.  
  11.         if (a[mid] == x) {
  12.             return mid;      
  13.         } else if (a[mid] < x) {
  14.             left = mid + 1; 
  15.         } else {
  16.             right = mid - 1; 
  17.         }
  18.     }
  19.  
  20.     return -1; 
  21. }
  22.  
  23. int main(void) {
  24.     int n, x, i;
  25.     int *a;
  26.     int ans = -1;
  27.  
  28.     if (scanf("%d %d", &n, &x) != 2) return -1;
  29.  
  30.     a = (int*)malloc(sizeof(int) * n);
  31.     if (a == NULL) {
  32.         printf("ERROR\n");
  33.         return -1;
  34.     }
  35.  
  36.     for (i = 0; i < n; i++) {
  37.         scanf("%d", &a[i]);
  38.     }
  39.  
  40.     ans = binary_search(a, n, x);
  41.  
  42.     if (ans != -1) {
  43.         printf("a[%d] = %d\n", ans, a[ans]);
  44.     } else {
  45.         printf("not found\n");
  46.     }
  47.  
  48.     free(a);
  49.     return 0;
  50. }
Success #stdin #stdout 0s 5320KB
comments (?)
stdin
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12 5
1 2 3 4 5 8 9 13 16 21 25 27
stdout
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a[4] = 5
https://ideone.com/biITzE
language:
C (gcc 8.3)
created:
2 days ago
visibility:
public

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