How to Solve It

#include <bits/stdc++.h>
using namespace std;
char fa[30],lson[30],rson[30];
int n;
void dfs(char u)
{
	if(u=='*') return;
	cout<<u;
	char a=u-'a'+1;
	if(lson[a]) dfs(lson[a]);
	if(rson[a]) dfs(rson[a]);
}
signed main()
{
	cin>>n;
	for(int i=1;i<=n;i++) cin>>fa[i]>>lson[i]>>rson[i];
	dfs(fa[1]);
	return 0;
}