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  1. //第3回 課題１
  2. #include <stdio.h>
  3. #include <stdlib.h>
  4.  
  5. //この関数を実装する
  6. int binary_search(int a[],int n,int x){
  7. 	//この関数の内側だけを書く
  8. 	    int left = 0;
  9.     int right = n - 1;
  10.  
  11.     while (left <= right) {
  12.         int mid = left + (right - left) / 2;
  13.  
  14.         if (a[mid] == x) {
  15.             return mid;  
  16.         } else if (a[mid] < x) {
  17.             left = mid + 1; 
  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. 	scanf("%d %d",&n,&x);
  31. 	a = (int*)malloc(sizeof(int)*n);
  32. 	if(a==NULL){
  33. 		printf("ERROR\n");
  34. 		return -1;
  35. 	}
  36. 	for(i=0;i<n;i++){
  37. 		scanf("%d",&a[i]);
  38. 	}
  39. 	ans = binary_search(a,n,x);
  40. 	if(ans != -1) printf("a[%d] = %d\n",ans,a[ans]);
  41. 	else printf("not found\n");
  42. 	free(a);
  43. 	return 0;
  44. }
Success #stdin #stdout 0.01s 5288KB
comments (?)
stdin 
12 5
1 2 3 4 5 8 9 13 16 21 25 27
stdout 
a[4] = 5
https://ideone.com/rD0EPn
language:
C (gcc 8.3)
created:
3 days ago
visibility:
public

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