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poj3067 Japan

編輯：關於C++

Description

Japan plans to welcome the ACM ICPC World Finals and a lot of roads must be built for the venue. Japan is tall island with N cities on the East coast and M cities on the West coast (M <= 1000, N <= 1000). K superhighways will be build. Cities on each coast are numbered 1, 2, ... from North to South. Each superhighway is straight line and connects city on the East coast with city of the West coast. The funding for the construction is guaranteed by ACM. A major portion of the sum is determined by the number of crossings between superhighways. At most two superhighways cross at one location. Write a program that calculates the number of the crossings between superhighways.

Input

The input file starts with T - the number of test cases. Each test case starts with three numbers – N, M, K. Each of the next K lines contains two numbers – the numbers of cities connected by the superhighway. The first one is the number of the city on the East coast and second one is the number of the city of the West coast.

Output

For each test case write one line on the standard output:
Test case (case number): (number of crossings)

Sample Input

Sample Output

Test case 1: 5

這題和star,cows差不多，把讀入的坐標看做x,y，那麼先按x進行升序排序，如果x相同的話就按照y升序排序。然後依次循環，加上比a[i].y大的線段的個數。注意用__int64

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
using namespace std;
#define maxn 3005
int b[maxn];
struct node{
	int x,y;
}a[maxn*maxn];

bool cmp(node a,node b){
	if(a.x==b.x)return a.y0){
		num+=b[pos];pos-=lowbit(pos);
	}
	return num;
}

int main()
{
	int n,m,i,j,T,k,num1=0;
	__int64 sum;
	scanf("%d",&T);
	while(T--)
	{
		scanf("%d%d%d",&n,&m,&k);
		for(i=1;i<=k;i++){
			scanf("%d%d",&a[i].x,&a[i].y);
			a[i].x++;a[i].y++;
		}
		sort(a+1,a+1+k,cmp);
		memset(b,0,sizeof(b));
		sum=0;
		for(i=1;i<=k;i++){
			sum+=i-1-getsum(a[i].y);
			update(a[i].y,1);
		}
		num1++;
		printf("Test case %d: %I64d\n",num1,sum);
	}
	return 0;
}