//第3回 課題１
#include <stdio.h>
#include <stdlib.h>
 
//この関数を実装する
int binary_search(int a[],int n,int x){
	//この関数の内側だけを書く
	int lef=0,rig=n-1;
	while(1){
	   int mid=(lef+rig)/2;
	   if(a[mid]==x){
	       return mid;
	       break;
       }else if(lef<rig){
	       if(a[mid]>x){
	       rig=mid-1;
	       }
	       if(a[mid]<x){
	       lef=mid+1;
	       }
	   }else{
	       return -1;
	       break;
	   }
	}
 
}
 
int main(void) {
	int n,x,i;
	int *a;
	int ans = -1;
	scanf("%d %d",&n,&x);
	a = (int*)malloc(sizeof(int)*n);
	if(a==NULL){
		printf("ERROR\n");
		return -1;
	}
	for(i=0;i<n;i++){
		scanf("%d",&a[i]);
	}
	ans = binary_search(a,n,x);
	if(ans != -1) printf("a[%d] = %d\n",ans,a[ans]);
	else printf("not found\n");
	free(a);
	return 0;
}
 

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