校园迷宫-rqnoj-195

和上面的八数码难题差不多，因为是求最优解，所以用队列，至于判重，把一个个坐标映射成一个整数。

#include<cstdio>#include<cstdlib>#include<cmath>#include<cstring>#include<map>#include<queue>#include<algorithm>using namespace std;const int maxn=2000+10;int a[maxn][maxn];int n,m;struct state{    int x,y;    int step;};state start,target;queue<state> q;map <int,int> hash;void init(){    freopen("input.txt","r",stdin);    freopen("output.txt","w",stdout);}int gethash(state st){    return st.x*m+st.y;}void readdata(){    scanf("%d%d",&n,&m);    for (int i=1;i<=n;i++)        for (int j=1;j<=m;j++)            scanf("%d",&a[i][j]);            //    printmap();    scanf("%d%d",&start.x,&start.y);    scanf("%d%d",&target.x,&target.y);    start.step=0;    q.push(start);    hash[gethash(start)]=1;}bool trytoinsert(state st){    int h=gethash(st);    if (hash[h]) return false;    hash[h]=1;    return true;}void check(state st){    if (gethash(st)==gethash(target))    {        printf("%d\n",st.step);        exit(0);    }}int dx[]={0,0,1,-1};int dy[]={1,-1,0,0};void expand(state cur, state &st,int i){    memcpy(&st,&cur,sizeof(cur));    st.x+=dx[i];    st.y+=dy[i];    st.step++;}void work(){    while (!q.empty())    {        state cur=q.front();        q.pop();        //printf("%d,%d,%d\n",cur.x,cur.y,cur.step);        for (int i=0;i<4;i++)        {            state st;            expand(cur,st,i);            if (a[st.x][st.y] || st.x<1 ||st.x>n ||st.y<1 || st.y>m) continue;            check(st);            if (trytoinsert(st)) q.push(st);        }    }    printf("No Answer!\n");}int main(){    //init();    readdata();    work();    return 0;}