wa code:

#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
const int N=123456789+100;
int a[N],b[N];
bool vis[N];
void bfs(int n,int k)
{
    int x,y,p,m=1;
    queue<int>q;
    q.push(n);
    vis[n]=true;
    int sum=1;
    while(!q.empty())
    {
        x=q.front();
        m=1;
        while(x>0)
        {
            y=x%10;
            for(int i=1;i<=k;i++)
            {
                if(a[i]==y)
                {
                    p=q.front()+(b[i]-y)*m;
                    if(!vis[p])
                    {
                        q.push(p);
                        vis[p]=true;
                        sum++;
                    }
                }
            }
            m*=10;
            x/=10;
        }
        q.pop();
    }
    printf("%d\n",sum);
    return ;
}
int main()
{
    int n,k;
    scanf("%d%d",&n,&k);
    for(int i=1;i<=k;i++)
    {
        scanf("%d%d",&a[i],&b[i]);
    }
    memset(vis,false,sizeof(vis));
    bfs(n,k);
    return 0;
}

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