1140.cpp

这是哈尔滨工业大学acmOJ的源代码

/*  This Code is Submitted by wywcgs for Problem 1140 on 2006-02-22 at 15:01:24 */ 
#include <cstdio>
#include <queue>
#include <climits>
#include <algorithm>
using namespace std;

typedef unsigned int uint;
const int MAX = 128;
const int DIR[][2] = { { -1, 0 }, { 0, -1 }, { 1, 0 }, { 0, 1 } };

char map[MAX][MAX];
int n, m;
uint step[MAX][MAX];
queue<int> Q;

inline bool legal(int x, int y) { return (x >= 0 && x <= n && y >= 0 && y <= m); }
uint play(int, int, int, int);
void update(int, int);

int main()
{
	int i, case_no, pair_no;
	
	for(case_no = 1; scanf("%d %d%*c", &m, &n) != EOF && n != 0; case_no++) {
		memset(map, 0, sizeof(map)); n++; m++;
		for(i = 1; i < n; i++) gets(map[i]+1);
		printf("Board #%d:\n", case_no);
		int bx, by, ex, ey;
		for(pair_no = 1; scanf("%d %d %d %d", &by, &bx, &ey, &ex) != EOF && bx != 0; pair_no++) {
			printf("Pair %d: ", pair_no);
			uint seg = play(bx, by, ex, ey);
			if(seg == UINT_MAX) printf("impossible.\n");
			else printf("%u segments.\n", seg);
		}
		putchar('\n');
	}
	
	return 0;
}

uint play(int bx, int by, int ex, int ey)
{
	while(!Q.empty()) Q.pop();
	memset(step, -1, sizeof(step));
	step[bx][by] = 0; update(bx, by);
	while(!Q.empty() && step[ex][ey] == UINT_MAX) {
		int p = Q.front(); Q.pop();
		update(p>>8, p&127);
	}
	return step[ex][ey];
}

void update(int x, int y)
{
	int i, j, lmt = max(n, m);
	for(i = 0; i < 4; i++)
		for(j = 1; j <= lmt; j++) {
			int cx = x+j*DIR[i][0], cy = y+j*DIR[i][1];
			if(!legal(cx, cy) || step[cx][cy] <= step[x][y]) break;
			uint b = step[cx][cy]; step[cx][cy] = step[x][y] + 1;
			if(map[cx][cy] == 'X') break;
			else if(b == UINT_MAX) Q.push((cx<<8)|cy);
		}
}