HDU 3647 Tetris （暴力DFS）

题意：给你十个俄罗斯方块，问你能否拼成指定长宽的矩形，方块下落的顺序是严格确定的，后下落的方块不能落在先下落的方块之下。

每个俄罗斯方块都是由更小的小方格拼成的， 可以用一个一维数组来记录每一列已经摞上了多少个小方格。DFS遵循底部放满原则，如果可以恰好和已存在的方块实现无缝拼接才往上放，否则回溯。

#include <iostream>
#include <cstring>

using namespace std;

char tet[20]; //记录方块的下降次序
int box[45]; //把方块分成小格子，记录每列有多个小格子
int m, n;

bool DFS( int cur )
{
    if ( cur == 10 ) return true;

    switch( tet[cur] )
    {
        case 'I' :
        for ( int i = 0; i < n; i++ )
        {
            if ( box[i] + 4 <= m )   //判断能不能竖着放
            {
                box[i] += 4;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 4;
            }
            if ( i + 3 < n && box[i] == box[i + 1] && box[i + 1] == box[i + 2] && box[i + 2] == box[i + 3] && box[i] + 1 <= m )    //能不能横着放
            {
                for ( int j = i; j < i + 4; j++ ) ++box[j];
                if ( DFS( cur + 1 ) ) return true;
                for ( int j = i; j < i + 4; j++ ) --box[j];
            }
        }
        break;

        case 'O':
        for ( int i = 0; i < n; i++ )
        {
            if ( i + 1 < n && box[i] == box[i + 1] && box[i] + 2 <= m )
            {
                box[i] += 2;
                box[i + 1] += 2;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 2;
                box[i + 1] -= 2;
            }
        }
        break;

        case 'L' :
        for ( int i = 0; i < n; i++ )
        {
            if ( i + 1 < n && box[i] + 3 <= m && box[i] == box[i + 1] )    //正着放L
            {
                box[i] += 3;
                box[i + 1] += 1;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 3;
                box[i + 1] -= 1;
            }

            if (i + 2 < n && box[i] + 1 == box[i + 1] && box[i + 1] == box[i + 2] && box[i] + 2 <= m && box[i + 1] + 1 <= m )    //顺时针旋转90°
            {
                box[i] += 2;
                box[i + 1] += 1;
                box[i + 2] += 1;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 2;
                box[i + 1] -= 1;
                box[i + 2] -= 1;
            }

            if (i + 1 < n && box[i] + 1 <= m && box[i + 1] + 3 <= m && box[i + 1] + 2 == box[i] )    //顺时针旋转180°
            {
                box[i] += 1;
                box[i + 1] += 3;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 1;
                box[i + 1] -= 3;
            }

            if (i + 2 < n && box[i] == box[i + 1] && box[i + 1] == box[i + 2] && box[i + 2] + 2 <= m )    //顺时针旋转270°
            {
                box[i] += 1;
                box[i + 1] += 1;
                box[i + 2] += 2;
                if ( DFS(cur + 1) ) return true;
                box[i] -= 1;
                box[i + 1] -= 1;
                box[i + 2] -= 2;
            }

        }
        break;

        case 'J' :
        for ( int i = 0; i < n; i++ )
        {
            if (i + 1 < n && box[i] == box[i + 1] && box[i + 1] + 3 <= m )         //0
            {
                box[i] += 1;
                box[i + 1] += 3;
                if ( DFS(cur + 1) ) return true;
                box[i] -= 1;
                box[i + 1] -= 3;
            }
            if (i + 2 < n && box[i] == box[i + 1] && box[i + 1] == box[i + 2] && box[i] + 2 <= m)         //90
            {
                box[i] += 2;
                box[i + 1] += 1;
                box[i + 2] += 1;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 2;
                box[i + 1] -= 1;
                box[i + 2] -= 1;
            }
            if (i + 1 < n && box[i] + 2 == box[i + 1] && box[i] + 3 <= m && box[i + 1] + 1 <= m )         //180
            {
                box[i] += 3;
                box[i + 1] += 1;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 3;
                box[i + 1] -= 1;
            }
            if (i + 2 < n && box[i] == box[i + 1] && box[i + 2] + 1 == box[i + 1] && box[i] + 1 <= m && box[i + 2] + 2 <= m)         //270
            {
                box[i] += 1;
                box[i + 1] += 1;
                box[i + 2] += 2;
                if ( DFS(cur + 1) ) return true;
                box[i] -= 1;
                box[i + 1] -= 1;
                box[i + 2] -= 2;
            }
        }
        break;

        case 'Z' :
        for ( int i = 0; i < n; i++ )
        {
            if (i + 2 < n && box[i + 2] == box[i + 1] && box[i + 1] + 1 == box[i] && box[i] + 1 <= m && box[i + 1] + 2 <= m )  //0
            {
                box[i] += 1;
                box[i + 1] += 2;
                box[i + 2] += 1;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 1;
                box[i + 1] -= 2;
                box[i + 2] -= 1;
            }
            if (i + 1 < n && box[i] + 1 == box[i + 1] && box[i] + 2 <= m && box[i + 1] + 2 <= m)   //90
            {
                box[i] += 2;
                box[i + 1] += 2;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 2;
                box[i + 1] -= 2;
            }
        }
        break;

        case 'S' :
        for ( int i = 0; i < n; i++ )
        {
            if (i + 2 < n && box[i] == box[i + 1] && box[i + 1] + 1 == box[i + 2] && box[i + 1] + 2 <= m && box[i + 2] + 1 <= m )    //0
            {
                box[i] += 1;
                box[i + 1] += 2;
                box[i + 2] += 1;
                if ( DFS(cur + 1) ) return true;
                box[i] -= 1;
                box[i + 1] -= 2;
                box[i + 2] -= 1;
            }
            if (i + 1 < n && box[i + 1] + 1 == box[i] && box[i] + 2 <= m && box[i + 1] + 2 <= m )    //90
            {
                box[i] += 2;
                box[i + 1] += 2;
                if ( DFS(cur + 1) ) return true;
                box[i] -= 2;
                box[i + 1] -= 2;
            }
        }
        break;

        case 'T' :
        for ( int i = 0; i < n; i++ )
        {
            if ( i + 2 < n && box[i] == box[i + 1] && box[i + 1] == box[i + 2] && box[i + 1] + 2 <= m ) //0
            {
                box[i] += 1;
                box[i + 1] += 2;
                box[i + 2] += 1;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 1;
                box[i + 1] -= 2;
                box[i + 2] -= 1;
            }

            if ( i + 1 < n && box[i] + 1 == box[i + 1] && box[i] + 3 <= m ) //90
            {
                box[i] += 3;
                box[i + 1] += 1;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 3;
                box[i + 1] -= 1;
            }
            if ( i + 2 < n && box[i] == box[i + 2] && box[i + 1] + 1 == box[i] && box[i + 1] + 2 <= m ) //180
            {
                box[i] += 1;
                box[i + 1] += 2;
                box[i + 2] += 1;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 1;
                box[i + 1] -= 2;
                box[i + 2] -= 1;
            }

            if ( i + 1 < n && box[i + 1] + 1 == box[i] && box[i + 1] + 3 <= m ) //270
            {
                box[i] += 1;
                box[i + 1] += 3;
                if ( DFS( cur + 1 ) ) return true;
                box[i] -= 1;
                box[i + 1] -= 3;
            }
        }
        break;
    }
    return false;
}

int main()
{
    while(cin>>n>>m&&n||m)
    {

        for(int i=0; i<10; i++)
            cin>>tet[i];

        memset(box, 0, sizeof(box));

        if(DFS(0))
            cout<<"Yes"<<endl;
        else
            cout<<"No"<<endl;

    }
    return 0;
}

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