USACO March. 2012

Connect the Cows

Times17

水题

Landscaping

Flowerpot

Tractor

广搜 搜到边界就可以终止了 没什么难度

#include <stdio.h>
#include <string.h>
#include <queue>
using namespace std;
const int MAX = 1010;
int a[MAX][MAX];
int dir[4][2] = {0,1,0,-1,1,0,-1,0};
struct node
{
	int x;
	int y;
	int step;
	bool friend operator < (node a,node b)
	{
		return a.step > b.step;
	}
}s;

void bfs()
{
	int i;
	s.step = 0;
	priority_queue <node> q;
	q.push(s);
	while(!q.empty())
	{
		node p = q.top();
		q.pop();
		if(p.x == 0 || p.y == 0 || p.x == 1001 || p.y == 1001)
		{
			printf("%d
",p.step);
			return;
		}
		for(i = 0;i < 4; i++)
		{
			node t;
			t.x = p.x + dir[i][0];
			t.y = p.y + dir[i][1];
			t.step = p.step;
			if(a[t.x][t.y] == -1)
				continue;
			if(a[t.x][t.y])
				t.step++;
			a[t.x][t.y] = -1;
			q.push(t);
		}
			
	}
}
int main()
{
	int n,x,y;
	scanf("%d %d %d",&n,&s.x,&s.y);
	while(n--)
	{
		scanf("%d %d",&x,&y);
		a[x][y] = 1;
	}
	bfs();
	return 0;
}

 

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