题解

#include<bits/stdc++.h>
using namespace std;
string qwq;
int s[33],num[33],k,nxt[33][16],qaq;
bool vis[10];
int ans[33];
void dfs(int x,int y)
{
	vis[x] = 1;
	if(vis[y])return;
	qaq++;
	for(int i = 1;i <= num[y];i++)
		dfs(y,nxt[y][i]);
}

void mul(){
	int jw = 0;
	for(int i = 30;i;i--)
	{
		ans[i] = ans[i] * qaq + jw;
		jw = ans[i] / 10;
		ans[i] %= 10;
	}
}

int main()
{
	ios::sync_with_stdio(0);
	cin.tie(NULL),cout.tie(NULL);
	ans[30] = 1;
	cin>>qwq>>k;
	int len = qwq.size();
	for(int i = 0;i < len;i++)
		s[i + 1] = qwq[i] - '0';
	for(int i = 1;i <= k;i++)
	{
		int x,y;
		cin>>x>>y;
		nxt[x][++num[x]] = y;
	}
	for(int i = 1;i <= len;i++)
	{
		qaq = 1;
		for(int j = 1;j <= num[s[i]];j++)
			dfs(s[i],nxt[s[i]][j]);
		memset(vis,0,sizeof(vis));
		mul();
	}
	int l = 0;
	for(;ans[l]==0;l++);
	for(int i = l;i <= 30;i++)
		cout<<ans[i];
	return 0;
}