poj1817 Traffic Jam

较难的bfs题目，广搜注意状态保存以便判重复和状态扩展。

#include <iostream>#include <queue>#include <set>#include <stdio.h>#include <string.h>using namespace std;int n,target_row,target_index;int dir[][2] = { {1,0} , {0,1}};  //下 右struct node{char box[10];int num;};char Encode(int r,int v,int d,int len){char a = v;a |= (r << 3);a |= ((len - 2) << 6);a |= (d << 7);return(a);}// 0表示下  1表示右inline int GetDir(char a){return ( (a & (1 << 7)) ? 1 : 0 );  }inline int GetLen(char a){return ( (a & (1 << 6)) ? 3 : 2 );  }inline int GetRow(char a){return( (a >> 3) & 7);}inline int GetVec(char a){return(a & 7);}int GetValue(node& a){int res = 0;for(int i =0; i < n; ++i){if(GetDir(a.box[i]) == 0)  // 竖直方向{res = res * 6 + GetRow(a.box[i]);}else{res = res * 6 + GetVec(a.box[i]);}}return(res);}void exact(node& a,char lab[][6]){int r,v,d,len;memset(lab,0,sizeof(char) * 36);for(int i = 0; i < n; ++i){r = GetRow(a.box[i]);v = GetVec(a.box[i]);d = GetDir(a.box[i]);len = GetLen(a.box[i]);for(int j = 0; j < len; ++j){lab[r][v] = 'a' + i;r += dir[d][0];v += dir[d][1];}}}int IsSuceed(node& a,char lab[][6]){int i = GetVec(a.box[target_index]) + GetLen(a.box[target_index]);for( ; i < 6 ; ++i){if(lab[target_row][i]){return(0);}}return(1);}int bfs(node a){set<int> visit;visit.insert(GetValue(a));queue<node> q;q.push(a);node nd1,nd2;char lab[6][6];int i,j;int r,v,d,len,r1,v1,value;while(q.empty() == 0){nd1 = q.front();  q.pop();exact(nd1,lab);if(IsSuceed(nd1,lab)){return(nd1.num + 1);}for(i = 0; i < n; ++i){nd2 = nd1;nd2.num += 1;r = GetRow(nd2.box[i]);v = GetVec(nd2.box[i]);d = GetDir(nd2.box[i]);len = GetLen(nd2.box[i]);//正向r1 = (d ? 0 : len) + r;v1 = (d ? len : 0) + v;for(j = 1; j <= 6; ++j){if(r1 >= 6 || v1 >= 6 || lab[r1][v1]) break;nd2.box[i] = Encode(r + j * dir[d][0],v + j * dir[d][1],d,len);r1 += dir[d][0];v1 += dir[d][1];value = GetValue(nd2);if(visit.find(value) == visit.end()){visit.insert(value);q.push(nd2);}}//反向nd2 = nd1;nd2.num += 1;for(j = 0; j < 6; ++j){r -= dir[d][0];v -= dir[d][1];if(r < 0 || v < 0 || lab[r][v]) break;nd2.box[i] = Encode(r,v,d,len);value = GetValue(nd2);if(visit.find(value) == visit.end()){visit.insert(value);q.push(nd2);}}}}return(-1);}int main(){node nd;int i,j,t,cnt = 0;int sr_index[10],sv_index[10],er_index[10],ev_index[10];int d,len;char vehicles[10][10]; while(cin >> n){if(n == 0) break;++cnt;memset(sr_index,-1,sizeof(sr_index));memset(sv_index,-1,sizeof(sv_index));for(i = 0; i < 6; ++i){cin >> vehicles[i];for(j = 0; j < 6; ++j){if(vehicles[i][j] == '.') continue;if(vehicles[i][j] == 'x'){if(sr_index[n - 1] == -1 && sv_index[n - 1] == -1){sr_index[n - 1] = i;sv_index[n - 1] = j;}else{er_index[n - 1] = i;ev_index[n - 1] = j; }}else{t = vehicles[i][j] - 'a';if(sr_index[t] == -1 && sv_index[t] == -1){sr_index[t] = i;sv_index[t] = j;}else{er_index[t] = i;ev_index[t] = j;}}}}target_index = n - 1;target_row = sr_index[target_index];for(i = 0; i < n; ++i){if(sr_index[i] == er_index[i]){d = 1;len = ev_index[i] - sv_index[i] + 1;}else{d = 0;len = er_index[i] - sr_index[i] + 1;}nd.box[i] = Encode(sr_index[i],sv_index[i],d,len);}for(j = GetVec(nd.box[target_index]) + GetLen(nd.box[target_index]); j < 6; ++j){if(vehicles[target_row][j] != '.' && GetDir(nd.box[vehicles[target_row][j] - 'a']) == 1){printf("You are trapped in scenario #%d.\n",cnt);break;}}if(j < 6)  continue;nd.num = 0;int res = bfs(nd);if(res == -1){printf("You are trapped in scenario #%d.\n",cnt);}else{printf("Scenario #%d requires %d moves.\n",cnt,res);}}return(0);}