CodeForces 828C String Reconstruction

#include <bits/stdc++.h>
using namespace std;
const int maxn = 1e6+100;
string s[maxn];
vector<pair<int,int> >tmp;
int main(void)
{
    int n,k,x;
    scanf("%d",&n);
    for(int i=0;i<n;i++)
    {
        cin>>s[i]>>k;
        for(int j=0;j<k;j++)
        {
            scanf("%d",&x);
            tmp.push_back(make_pair(x,i));
        }
    }
    sort(tmp.begin(),tmp.end());
    string ans;
    int len = 1;
    for(unsigned i = 0;i<tmp.size();i++)
    {
        int t1 = tmp[i].first,t2 = tmp[i].second;
        while(t1>len)
        {
            ans += 'a';
            len++;
        }
        //len-t1可以避免重复添加
        for(unsigned j = len-t1;j<s[t2].length();j++)
        {
            ans += s[t2][j];
            len++;
        }
    }
    cout<<ans<<endl;
    return 0;
}