洛谷 2346 四子连棋 bfs

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题目：
https://www.luogu.org/problem/show?pid=2346

40分钟打出代码（80分）+5个小时调试=AC

水题，没有任何技巧的bfs，注意状态的储存；

目标状态：横竖斜4个同色；

but！由于忘了判竖着的情况，所以一直80，调了5、6个小时？；
洛谷不让下数据……所以只能手算……然后和电脑比较答案……；
不过这个题用来练bfs挺好的

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<queue>using namespace std;const int mod=131373,base=137;bool vis[2000005];struct hh {    int a[8][8],x1,y1,x2,y2,step,up;}star;string s[8];//1 hei ,2 bai;queue<hh>q;int ans,X[6]={0,1,0,-1,0},Y[6]={0,0,-1,0,1},fx,fy;int hashs(hh now){    int tot=0;    for(int i=1;i<=4;i++)        for(int j=1;j<=4;j++)            tot=(base*tot+(int)now.a[i][j])%mod;    return tot;}bool pd(hh now){    if(now.a[2][2]==now.a[1][1] && now.a[3][3]==now.a[1][1] && now.a[4][4]==now.a[1][1]) return true;    for(int i=1;i<=4;i++)    {        if(now.a[i][1]==now.a[i][2] && now.a[i][1]==now.a[i][3] && now.a[i][1]==now.a[i][4]) return true;        if(now.a[1][i]==now.a[2][i] && now.a[1][i]==now.a[3][i] && now.a[1][i]==now.a[4][i]) return true;    }    return false;}int bfs(){    memset(vis,0,sizeof(vis));    while(!q.empty()) q.pop();    q.push(star),vis[hashs(star)]=1;    while(!q.empty())    {        hh now=q.front(),nxt;        q.pop();        if(pd(now)) return now.step;        else        {            for(int i=1;i<=8;i++)            {                if(i<=4) fx=now.x1+X[i],fy=now.y1+Y[i];                else fx=now.x2+X[i-4],fy=now.y2+Y[i-4];                nxt=now;                if(now.a[fx][fy]!=now.up || fx<1 || fx>4 || fy<1 || fy>4) continue;                if(i<=4) swap(nxt.a[fx][fy],nxt.a[now.x1][now.y1]);                else swap(nxt.a[fx][fy],nxt.a[now.x2][now.y2]);                if(!vis[hashs(nxt)])                {                    if(i<=4) nxt.x1=fx,nxt.y1=fy;                    else nxt.x2=fx,nxt.y2=fy;                    vis[(hashs(nxt))]=1;                    if(now.up & 1) nxt.up=2;                    else nxt.up=1;                    nxt.step=now.step+1;                    q.push(nxt);                }            }        }    }}void solve(){    for(int i=1;i<=4;i++)    {        cin>>s[i];        for(int j=0;j<4;j++)            if(s[i][j]=='B') star.a[i][j+1]=1;            else if(s[i][j]=='W') star.a[i][j+1]=2;            else if(star.x1) star.x2=i,star.y2=j+1;            else star.x1=i,star.y1=j+1;    }    star.up=1,ans=bfs(),star.up=2;    cout<<min(bfs(),ans);    return;}int main(){    solve();    return 0;}

2017.10.26 感谢Sher_lock指出BUG；
修改后的

#include<iostream>#include<cstdio>#include<cstring>#include<algorithm>#include<queue>using namespace std;const int mod=131373,base=137;bool vis[2000005];struct hh {    int a[8][8],x1,y1,x2,y2,step,up;}star;string s[8];//1 hei ,2 bai;queue<hh>q;int ans,X[6]={0,1,0,-1,0},Y[6]={0,0,-1,0,1},fx,fy;int hashs(hh now){    int tot=0;    for(int i=1;i<=4;i++)        for(int j=1;j<=4;j++)            tot=(base*tot+(int)now.a[i][j])%mod;    return tot;}bool pd(hh now){    if(now.a[2][2]==now.a[1][1] && now.a[3][3]==now.a[1][1] && now.a[4][4]==now.a[1][1]) return true;    if(now.a[1][4]==now.a[2][3] && now.a[3][2]==now.a[1][4] && now.a[4][1]==now.a[1][4]) return true;    for(int i=1;i<=4;i++)    {        if(now.a[i][1]==now.a[i][2] && now.a[i][1]==now.a[i][3] && now.a[i][1]==now.a[i][4]) return true;        if(now.a[1][i]==now.a[2][i] && now.a[1][i]==now.a[3][i] && now.a[1][i]==now.a[4][i]) return true;    }    return false;}int bfs(){    memset(vis,0,sizeof(vis));    while(!q.empty()) q.pop();    q.push(star),vis[hashs(star)]=1;    while(!q.empty())    {        hh now=q.front(),nxt;        q.pop();        if(pd(now)) return now.step;        else        {            for(int i=1;i<=8;i++)            {                if(i<=4) fx=now.x1+X[i],fy=now.y1+Y[i];                else fx=now.x2+X[i-4],fy=now.y2+Y[i-4];                nxt=now;                if(now.a[fx][fy]!=now.up || fx<1 || fx>4 || fy<1 || fy>4) continue;                if(i<=4) swap(nxt.a[fx][fy],nxt.a[now.x1][now.y1]);                else swap(nxt.a[fx][fy],nxt.a[now.x2][now.y2]);                if(!vis[hashs(nxt)])                {                    if(i<=4) nxt.x1=fx,nxt.y1=fy;                    else nxt.x2=fx,nxt.y2=fy;                    vis[(hashs(nxt))]=1;                    if(now.up & 1) nxt.up=2;                    else nxt.up=1;                    nxt.step=now.step+1;                    q.push(nxt);                }            }        }    }}void solve(){    for(int i=1;i<=4;i++)    {        cin>>s[i];        for(int j=0;j<4;j++)            if(s[i][j]=='B') star.a[i][j+1]=1;            else if(s[i][j]=='W') star.a[i][j+1]=2;            else if(star.x1) star.x2=i,star.y2=j+1;            else star.x1=i,star.y1=j+1;    }    star.up=1,ans=bfs(),star.up=2;    cout<<min(bfs(),ans);    return;}int main(){    solve();    return 0;}

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