pots（bfs）

#include <stdio.h>
#include <algorithm>
#include <cstring>
using namespace std;
int A,B,C,vis[101][101];
char str[6][10] = {"FILL(1)", "FILL(2)", "DROP(1)", "DROP(2)", "POUR(1,2)", "POUR(2,1)"};
structnode
{
    int num,a,b;
    node *pre;
};
node que[101*101];
void print(node now)
{
    if (now.pre)
    {
        print(*now.pre);
        printf("%s\n",str[now.num]);
    }
}
void BFS()
{
    int step=0,head=0,tail=1,count,water1,water2;
    que[0].a=que[0].b=0;
    que[0].pre=0;
    while (tail-head>0)
    {
        count=tail-head;
        while (count--)
        {
            node now=que[head];
            if (now.a==C || now.b==C)
            {
                printf("%d\n",step);
                print(now);
                return;
            }
            if(!vis[A][now.b])
            {
                vis[A][now.b]=1;
                que[tail].num=0;
                que[tail].a=A;
                que[tail].b=now.b;
                que[tail++].pre=&que[head];
            }
            if(!vis[now.a][B])
            {
                vis[now.a][B]=1;
                que[tail].num=1;
                que[tail].a=now.a;
                que[tail].b=B;
                que[tail++].pre=&que[head];
            }
            if(!vis[0][now.b])
            {
                vis[A][now.b]=1;
                que[tail].num=2;
                que[tail].a=0;
                que[tail].b=now.b;
                que[tail++].pre=&que[head];
            }
            if(!vis[now.a][0])
            {
                vis[now.a][0]=1;
                que[tail].num=3;
                que[tail].a=now.a;
                que[tail].b=0;
                que[tail++].pre=&que[head];
            }
            water1=min (now.a,B-now.b);
            if(!vis[now.a-water1][now.b+water1])
            {
                vis[now.a-water1][now.b+water1]=1;
                que[tail].num=4;
                que[tail].a=now.a-water1;
                que[tail].b=now.b+water1;
                que[tail++].pre=&que[head];
            }
            water2=min (A-now.a,now.b);
            if(!vis[now.a+water2][now.b-water2])
            {
                vis[now.a+water2][now.b-water2]=1;
                que[tail].num=5;
                que[tail].a=now.a+water2;
                que[tail].b=now.b-water2;
                que[tail++].pre=&que[head];
            }
            head++;
        }
        step++;
    }
    printf("impossible\n");
}
int main ()
{
    scanf("%d%d%d",&A,&B,&C);
    memset(vis,0,sizeof(vis));
    vis[0][0]=1;
    BFS();
    return 0;
}