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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.     return -1;
  20. }
  21.  
  22. int main(void) {
  23.     int n,x,i;
  24.     int *a;
  25.     int ans = -1;
  26.  
  27.     scanf("%d %d",&n,&x);
  28.     a = (int*)malloc(sizeof(int)*n);
  29.     if(a==NULL){
  30.         printf("ERROR\n");
  31.         return -1;
  32.     }
  33.  
  34.     for(i=0;i<n;i++){
  35.         scanf("%d",&a[i]);
  36.     }
  37.  
  38.     ans = binary_search(a,n,x);
  39.  
  40.     if(ans != -1) printf("a[%d] = %d\n",ans,a[ans]);
  41.     else printf("not found\n");
  42.  
  43.     free(a);
  44.     return 0;
  45. }
  46.  
Success #stdin #stdout 0s 5296KB
comments (?)
stdin 
12 5
1 2 3 4 5 8 9 13 16 21 25 27
stdout 
a[4] = 5
https://ideone.com/yQZWzL
language:
C (gcc 8.3)
created:
1 day ago
visibility:
public

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