binary search

#include<cstdio>
//二分查找  算法笔记 例子
const int n=10;
int binaryserach(int a[],int left,int right,int x){
	int mid;
	while(left <= right){
		mid=(left+right)/2;
		if(a[mid] == x) return mid;
		else if( a[mid]< x) left =mid+1;
		else right =mid-1;
	}
	return -1;
}
int main(){
	int a[n]={1,3,4,6,7,8,10,11,12,15};
	int m;
	while( scanf("%d",&m) !=EOF){
		int x=binaryserach(a ,0,n-1,m);
		printf("%d\n",x);
	} 

	return 0;
} 

算法笔记 装水问题
#include<cstdio>
#include<cmath>
const double PI =acos(-1.0);
const double eps = 1e-5;//精度
double f( double R,double h){
	double alpha = 2* acos( (R-h) /R);
	double L = 2*sqrt(R *R -(R-h) *(R-h));
	double S1 = alpha  *R *R/2 - L*(R- h)/2;
	double S2 = PI *R *R/2;
	return S1/S2;
} 
double solve( double R,double r){
	double left =0,right =R,mid;
	while( right - left >eps){
		mid = (left + right) /2;
		if( f(R,mid) > r){
			right = mid;
		}else{
			left =mid;
		}
	}
	return mid;
}
int main(){
	double R,r;
	scanf("%lf%lf",&R,&r);
	printf("%.4f\n", solve(R ,r ));
	return 0;
}