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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.     int mid;
  8.  
  9.     while(left <= right){
  10.         mid = (left + right) / 2;
  11.  
  12.         if(a[mid] == x){
  13.             return mid;
  14.         }
  15.         else if(a[mid] < x){
  16.             left = mid + 1;
  17.         }
  18.         else{
  19.             right = mid - 1;
  20.         }
  21.     }
  22.  
  23.     return -1;
  24. }
  25.  
  26. int main(void) {
  27.     int n, x, i;
  28.     int *a;
  29.     int ans = -1;
  30.  
  31.     scanf("%d %d", &n, &x);
  32.  
  33.     a = (int*)malloc(sizeof(int) * n);
  34.     if(a == NULL){
  35.         printf("ERROR\n");
  36.         return -1;
  37.     }
  38.  
  39.     for(i = 0; i < n; i++){
  40.         scanf("%d", &a[i]);
  41.     }
  42.  
  43.     ans = binary_search(a, n, x);
  44.  
  45.     if(ans != -1)
  46.         printf("a[%d] = %d\n", ans, a[ans]);
  47.     else
  48.         printf("not found\n");
  49.  
  50.     free(a);
  51.     return 0;
  52. }
  53.  
Success #stdin #stdout 0.01s 5284KB
comments (?)
stdin 
12 5
1 2 3 4 5 8 9 13 16 21 25 27
stdout 
a[4] = 5
https://ideone.com/EZfFLN
language:
C (gcc 8.3)
created:
1 day ago
visibility:
public

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