[CodeForces]String Reconstruction

http://codeforces.com/contest/828/problem/C

并查集的神奇应用。

#include<bits/stdc++.h>
using namespace std;

const int maxn=10000005;
char s[maxn];
string ss[100000];
vector<int> g[100000];
int fa[maxn];

int findfa(int x)
{
    if (fa[x]==x) return x;
    else return fa[x]=findfa(fa[x]);
}

void merge(int u,int v)
{
    int f1=findfa(u);
    int f2=findfa(v);
    if (f1!=f2)
    {
        fa[f1]=f2;
    }
}

int main()
{
    int n;
    scanf("%d",&n);
    int ma=0;
    for (int i=0;i<n;i++)
    {
        cin >>ss[i];
        int k;
        scanf("%d",&k);
        int l=ss[i].length();
        for (int j=0;j<k;j++)
        {
            int x;
            scanf("%d",&x);
            g[i].push_back(x);
            if (x+l-1>ma) ma=x+l-1;
        }
    }
    s[ma+1]=0;
    for (int i=0;i<=ma+1;i++) fa[i]=i;
    for (int i=0;i<n;i++)
    {
        for (int j=0;j<g[i].size();j++)
        {
            int p=g[i][j];
            for (int k=findfa(p);k<=p+ss[i].length()-1;k=findfa(k+1))
            {
                s[k]=ss[i][k-p];
                merge(k,p+ss[i].length());
            }
        }
    }
    for (int i=1;i<=ma;i++)
        if (s[i]==0) s[i]='a';
    printf("%s",s+1);
    return 0;
}