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  1. #include <stdio.h>
  2.  
  3. // 二分探索関数
  4. int binary_search(int a[], int n, int x){
  5.     int left = 0;
  6.     int right = n - 1;
  7.     int mid;
  8. 	while(left <= right){mid = (left + right) / 2;
  9. 		if(a[mid] == x){return mid;}
  10.         else if(a[mid] < x){left = mid + 1;}
  11.         else{right = mid - 1;}}
  12.     return -1;}
  13. int main(){
  14.     int a[100];
  15.     int n, x, i;
  16.     int ans;
  17.     scanf("%d %d", &n, &x);
  18.     for(i = 0; i < n; i++){scanf("%d", &a[i]);}
  19.     ans= binary_search(a, n, x);
  20. 	if(ans != -1)  printf("a[%d] = %d\n", ans, a[ans]);
  21.     else printf("not found\n");
  22. 		return 0;}
Success #stdin #stdout 0s 5320KB
comments (?)
stdin
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5 50
10 20 30 40 50
stdout
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a[4] = 50
https://ideone.com/K2nfTK
language:
C (gcc 8.3)
created:
15 hours ago
visibility:
public

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