usaco-3.2-msquare-pass

呵呵，这个题目有点意思，要用bfs：

/*
ID: qq104801
LANG: C++
TASK: msquare
*/

#include <iostream>
#include <fstream>
#include <queue>
#include <set>
#include <string>
#include <algorithm>

using namespace std;

struct node{
    int d;
    string st,str;
    node(string _st,string _str,int _d)
    {st=_st;str=_str;d=_d;}
};
string end="";
set<string> ss;
queue<node> q;

node bfs()
{
    string x="12345678";
    if(end==x)return node("","",0);
    q.push(node(x,"",0));
    ss.insert(x);
    while(!q.empty())
    {
        node curr=q.front();
        q.pop();
        string c=curr.st;
        string a(c.rbegin(),c.rend());
        if(a==end) return node(a,curr.str+"A",curr.d+1);
        if(!ss.count(a))
        {
            ss.insert(a);
            q.push(node(a,curr.str+"A",curr.d+1));
        }

        string b(c[3]+c.substr(0,3)+c.substr(5)+c[4]);
        if(b==end)return node(b,curr.str+"B",curr.d+1);
        if(!ss.count(b))
        {
            ss.insert(b);
            q.push(node(b,curr.str+"B",curr.d+1));
        }
        swap(c[1],c[2]);swap(c[1],c[5]);swap(c[1],c[6]);
        if(c==end)return node(c,curr.str+"C",curr.d+1);
        if(!ss.count(c))
        {
            ss.insert(c);
            q.push(node(c,curr.str+"C",curr.d+1));
        }
    }
}

void test()
{    
    freopen("msquare.in","r",stdin);
    freopen("msquare.out","w",stdout);

    char c;
    for(int i=0;i<8;i++){
        cin>>c;
        end+=c;
    }
    node n=bfs();
    cout<<n.d<<endl<<n.str<<endl;
}

int main () 
{        
    test();        
    return 0;
}

test data

USACO Training
Grader Results     
8 users online
CHN/4 KGZ/1 MYS/1 SGP/1 TTO/1

USER: cn tom [qq104801]
TASK: msquare
LANG: C++

Compiling...
Compile: OK

Executing...
   Test 1: TEST OK [0.019 secs, 3524 KB]
   Test 2: TEST OK [0.003 secs, 3524 KB]
   Test 3: TEST OK [0.016 secs, 3524 KB]
   Test 4: TEST OK [0.005 secs, 3524 KB]
   Test 5: TEST OK [0.046 secs, 4052 KB]
   Test 6: TEST OK [0.092 secs, 4712 KB]
   Test 7: TEST OK [0.159 secs, 5636 KB]
   Test 8: TEST OK [0.270 secs, 6032 KB]

All tests OK.

YOUR PROGRAM ('msquare') WORKED FIRST TIME! That's fantastic -- and a rare thing. Please accept these special automated congratulations.

Here are the test data inputs:

------- test 1 ----
2 6 8 4 5 7 3 1
------- test 2 ----
1 2 3 4 5 6 7 8
------- test 3 ----
6 7 4 1 8 5 2 3
------- test 4 ----
5 1 2 4 3 7 8 6
------- test 5 ----
6 1 5 4 3 2 7 8
------- test 6 ----
4 1 2 3 5 8 7 6
------- test 7 ----
3 4 2 1 5 6 7 8
------- test 8 ----
4 3 1 2 5 6 7 8

Keep up the good work!
Thanks for your submission!