二分查找总结

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn=100008;
int a[maxn];
int n;
int bs(int x)
{
	int left=1,right=n;
	while(left<=right)
	{
		int mid=(left+right)>>1;
		if(a[mid]==x)
			right=mid-1;
		else	if(a[mid]>x)
			right=mid-1;
		else
			left=mid+1;
	}
	return left+1;
}
int main()
{
	int i,j,t,q,x,y;
	scanf("%d",&t);
	int cas=1;
	while(t--)
	{
		scanf("%d%d",&n,&q);
		for(i=1;i<=n;i++)
			scanf("%d",&a[i]);
		sort(a+1,a+1+n);
		printf("Case %d:\n",cas++);
		while(q--)
		{
			scanf("%d%d",&x,&y);
			int left=bs(x);
			int right=bs(y+1);
			printf("%d\n",right-left);
		}
	}
	return 0;
}