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咋回事

Posted by pcoat at 2008-08-07 18:58:07 on Problem 1328
实在是撑不住了,在这里问下
我是这样想的, 先把所有island排序,然后从左往右,
先放一个能覆盖第一个island的最右边的rader,然后看第二个能不能被覆盖,如果能,就算了,
否则再放能覆盖第二个island的最右边的rader,。。。一直下去
但是为何就wa,我觉得和大家用得那个分段区间也差不多。 为啥??
#include<stdio.h>
#include<math.h>
int main(){
	int n;
	float d;
	int i,j, k;
	int ct ;
	int step= 0;
	float a[1000];
	float x[1000];
	float y[1000]; 
	float tmp;
	bool flag = true;
	while(scanf("%d %f", &n, &d)!=EOF && (n!=0 ||d!=0) ){
		flag = true;
		for(i=0; i<n; i++){
			scanf("%f %f", &x[i], &y[i]);
			if(y[i] > d)
				flag = false; 
		}
		if(flag == false || d<=0){
			printf("Case %d: %d\n", step, -1);
			continue;	
		}

		for(i=0; i<n ; i++)
			for(j=i+1; j<n; j++)
				if(x[i] > x[j]){
					tmp = x[j];	x[j] = x[i]; x[i] = tmp;
					tmp = y[j]; y[j] = y[i]; y[i] = tmp;
				}

		ct = 0;
		a[ct++] = sqrt(d*d-y[0]*y[0]) + x[0];
		for(i=1; i<n; i++){
			if((x[i]-a[i-1])*(x[i]-a[i-1])+y[i]*y[i] > d*d){
				a[ct++] = sqrt(d*d-y[i]*y[i]) + x[i];
			}
		}
		printf("Case %d: %d\n", ++step, ct);
	}
	return 0;
}

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