zoj 1083 Frame Stacking

#include <iostream>#include <cstring>#include <cstdio>using namespace std;const int SIZE=30,NUM=26;struct square{int up, right, down, left;}alpha[NUM];int N,M,cnt,id[NUM];//cnt 图的种类数目，id[i]表示顶点i的入度bool cover[SIZE][SIZE][NUM],map[NUM][NUM],exist[NUM];//cover[i][j][k]表示(i, j)处可以是图片k,map[i][j]表示图片i在图片j的下方;exist[i]表示i是否存在于给定的图中char pic[SIZE][SIZE+1],seq[NUM];//seq储存的是得到的拓扑序列void read_map(){cnt=0;memset(exist, 0, sizeof exist);memset(alpha, -1, sizeof alpha);for(int i=0;i<N;++i)     {scanf("%s",pic[i]);for(int j=0;j<M;++j)               if(pic[i][j]!='.')               {                    int tmp=pic[i][j]-'A';                    if(!exist[tmp])                    {                         exist[tmp]=1;                          ++cnt;                    }                    //记录某个图片的上下边界。                    if(alpha[tmp].up == -1 || i < alpha[tmp].up)                         alpha[tmp].up = i;                    if(alpha[tmp].down == -1 || i > alpha[tmp].down)                         alpha[tmp].down = i;                    if(alpha[tmp].left == -1 || j < alpha[tmp].left)                         alpha[tmp].left = j;                    if(alpha[tmp].right == -1 || j > alpha[tmp].right)                         alpha[tmp].right = j;               }}}void inite(){     int i, j;     for(i=0;i<NUM;++i)     //复原每一个图片          if(exist[i])          {//如果第i个图存在则把图i的边界都赋值为1（由于图是环形的特性）               for(j = alpha[i].left; j <= alpha[i].right; ++j)//把两个上下边标记为1;                    cover[ alpha[i].up ][j][i] = cover[ alpha[i].down ][j][i] = 1;               for(j = alpha[i].up + 1; j < alpha[i].down; ++j)//把左右两个边标记为1;                    cover[j][ alpha[i].left ][i] = cover[j][ alpha[i].right ][i] = 1;          }}void build_map(){int i,j,k;memset(cover,0,sizeof cover);memset(id,0,sizeof id);memset(map,0,sizeof map);inite();     for(i=0; i<N; ++i)     {for(j=0; j<M; ++j){     if(pic[i][j] != '.')               {                    int tmp = pic[i][j]-'A';//第(i, j)位置，存放的类型                    for(k = 0; k < NUM; ++k)//建立有向图                         if(tmp != k && cover[i][j][k] && !map[k][tmp])                         {                              map[k][tmp] = 1;                              ++id[tmp];                         }               }}}}void toposort(int cur)//cur表示在拓扑序列中存在的元素个数;利用了深搜的特性{int i,j;if(cur == cnt)     {for(i = 0; i<cur; ++i)               putchar(seq[i]);puts("");return ;}for(i = 0; i < NUM; ++i)          if(exist[i] && !id[i])//找入度为零的顶点，也即是在当前情况下，最底下的定点;          {               id[i] = -1;               seq[cur] = i+'A';               for(j = 0;j < NUM; ++j)                    if(map[i][j])                         --id[j];               toposort(cur+1);               id[i] = 0;               for(j=0; j<NUM; ++j)                    if(map[i][j])                         ++id[j];          }}int main(){while(~scanf("%d %d",&N,&M))     {read_map();build_map();toposort(0);}return 0;}