【map|BFS】BZOJ 1627 [Usaco2007 Dec]穿越泥地

#include <cstdio>
#include <algorithm>
#include <cstring>
#include <queue>
#include <map>
using namespace std;

struct node{
    int x,y,step;
}point[100005],Start;

map<pair<int,int>,bool>vis;
map<pair<int,int>,bool>Map;

int fx[]={0,0,-1,0,1},fy[]={0,-1,0,1,0};
int Sx,Sy,n,step;

void BFS(){
    queue<node>Q;
    vis[make_pair(0,0)]=1;
    Start.x=0;
    Start.y=0;
    Start.step=0;
    Q.push(Start);
    while( !Q.empty() ){
        node now = Q.front();
        Q.pop();
        for(int i=1;i<=4;i++){
            int tx = now.x + fx[i];
            int ty = now.y + fy[i];
            if(tx==Sx && ty==Sy){
                printf("%d\n",now.step+1);
                return;
            }
            if(Map[make_pair(tx,ty)] || vis[make_pair(tx,ty)]) continue;
            node sb;
            sb.x=tx;
            sb.y=ty;
            vis[make_pair(tx,ty)]=1;
            sb.step=now.step+1;
            Q.push(sb);
        }
    }
}

void init(){
    scanf("%d%d%d",&Sx,&Sy,&n);
    for(int i=1;i<=n;i++){
        int a,b;
        scanf("%d%d",&a,&b);
        Map[make_pair(a,b)]=1;
    }
}

int main(){
    init();
    BFS();
    return 0;
}