代码：

#include<iostream>
#include<stdio.h>
#include<queue>
using namespace std;
int row,col,t;
char Map[22][22];
int flag[2048][22][22];
int startX,startY;
int move[][2]={{1,0},{0,-1},{-1,0},{0,1}};
int tempKey,num;
struct NodePoint{
 int nodeX,nodeY;
 int key;
 int time;
};

bool judge(NodePoint node){
 if(node.nodeX<0||node.nodeX>=row||node.nodeY<0||node.nodeY>=col||Map[node.nodeX][node.nodeY]==‘*‘)
  return false;
 else
  return true;
}

int escape(){
queue<NodePoint>q;
 while(!q.empty())
        q.pop();
NodePoint temp,front;
front.nodeX = startX;
front.nodeY = startY;
front.time = 0;
front.key = 0;
q.push(front);
while(!q.empty()){
 front=q.front();
 q.pop();
 for(int i=0;i<4;i++){
        temp.nodeX = front.nodeX;
     temp.nodeY = front.nodeY;
     temp.key = front.key;
  temp.nodeX+=move[i][0];
  temp.nodeY+=move[i][1];
  temp.time =front.time+1;
  if(temp.time>=t)//之前放在for 前面，一直wa，原因：
  return -1;//当^出现在第一个位置时，不能结束，导致t时刻它还能逃跑，如果^不在第一个位置则正确
  if(judge(temp)){
   if(Map[temp.nodeX][temp.nodeY]==‘^‘)
    return temp.time;
   if(Map[temp.nodeX][temp.nodeY]==‘@‘||Map[temp.nodeX][temp.nodeY]==‘.‘){
    if(!flag[temp.key][temp.nodeX][temp.nodeY]){
     flag[temp.key][temp.nodeX][temp.nodeY]=1;
     q.push(temp); 
                }
                continue;
   }
   if((Map[temp.nodeX][temp.nodeY]>=‘A‘&&Map[temp.nodeX][temp.nodeY]<=‘J‘)&&!flag[temp.key][temp.nodeX][temp.nodeY]){
    num = Map[temp.nodeX][temp.nodeY]-‘A‘;
    if((temp.key>>num)&1){
     flag[temp.key][temp.nodeX][temp.nodeY]=1;
     q.push(temp);
     
                }
                continue;
   }
   if(Map[temp.nodeX][temp.nodeY]>=‘a‘&&Map[temp.nodeX][temp.nodeY]<=‘j‘){
    num = Map[temp.nodeX][temp.nodeY]-‘a‘;
    tempKey=1<<num;
    temp.key = temp.key|tempKey;
    if(flag[temp.key][temp.nodeX][temp.nodeY]!=1){
     flag[temp.key][temp.nodeX][temp.nodeY]=1;
     q.push(temp);
     
                }
                continue;
   }
  }
 }
}
return -1;
}

int main(){
 while(~scanf("%d%d%d",&row,&col,&t)){
        bool ff = false;
  for(int i=0;i<row;i++){
    scanf("%s",Map[i]);
                if(!ff)
                {
                    for(int j=0;j<col;j++)
                    {
                        if(Map[i][j]==‘@‘)
                        {
                            startX=i;
                            startY=j;
                            ff=true;
                            break;
                        }
                    }
                }
   }
  memset(flag,0,sizeof(flag));
  flag[0][startX][startY]=1;
  printf("%d\n",escape());
 }
return 0;
}
/*
#include<iostream>
#include<stdio.h>
#include<string.h>
#include<queue>
using namespace std;
int dir[][2]={{1,0},{0,1},{-1,0},{0,-1}};
struct node
{
    int x,y;
    int cnt;
    int time;
};
char map[22][22];
int flag[2048][22][22];
int x1,y1;
int row,col,t;
queue<node>q;

bool judge(node tp)
{
    if(tp.x<0 || tp.x>=row || tp.y<0 || tp.y>=col || map[tp.x][tp.y]==‘*‘)
        return false;
    return true;
}

int bfs()
{
    while(!q.empty())
        q.pop();
    node temp,p;
    int i,cc;
    p.x=x1;
    p.y=y1;
    p.cnt=0;
    p.time=0;
    q.push(p);
    while(!q.empty())
    {
        p=q.front();
        q.pop();
        if(p.time>=t-1)
            return -1;
        for(i=0;i<4;i++)
        {
            temp=p;
            temp.x+=dir[i][0];
            temp.y+=dir[i][1];
            temp.time=p.time+1;
            temp.cnt=p.cnt;
            if(!judge(temp))
                continue;
            if(map[temp.x][temp.y]==‘^‘)
            {
                return temp.time;
            }
            if(map[temp.x][temp.y]==‘@‘ || map[temp.x][temp.y]==‘.‘)
            {
                if(!flag[temp.cnt][temp.x][temp.y])
                {
                    flag[temp.cnt][temp.x][temp.y]=1;
                    q.push(temp);
                }
                continue;
            }
            if(map[temp.x][temp.y]>=‘A‘ && map[temp.x][temp.y]<=‘J‘ && !flag[temp.cnt][temp.x][temp.y])
            {
                cc=temp.cnt;
                if((cc>>(map[temp.x][temp.y]-‘A‘)) & 1)
                {
                    flag[temp.cnt][temp.x][temp.y]=1;
                    printf("A~J\n");
                    q.push(temp);
                }
                continue;
            }
            if(map[temp.x][temp.y]>=‘a‘ && map[temp.x][temp.y]<=‘j‘)
            {
                cc=1<<(map[temp.x][temp.y]-‘a‘);
                temp.cnt=cc | temp.cnt;
                if(!flag[temp.cnt][temp.x][temp.y])
                {
                    flag[temp.cnt][temp.x][temp.y]=1;
                    printf("a~j\n");
                    q.push(temp);
                }
                continue;
            }
        }
    }
    return -1;
}

int main()
{
    while(~scanf("%d%d%d",&row,&col,&t))
    {
        int i,j;
        bool ff=false;
        for(i=0;i<row;i++)
        {
            scanf("%s",map[i]);
            if(!ff)
            {
                for(j=0;j<col;j++)
                {
                    if(map[i][j]==‘@‘)
                    {
                        x1=i;
                        y1=j;
                        ff=true;
                        break;
                    }
                }
            }
        }
        memset(flag,0,sizeof(flag));
        flag[0][x1][y1]=1;
        int res=bfs();
        printf("%d\n",res);
    }
    return 0;
}
*/

杭电胜利大逃亡续