CF501B Misha and Changing Handles solution

CF501B Misha and Changing Handles

思路

通过并差集，将旧名字的父亲设为新名字。将每个没出现过的旧名字加入初始名字。最后查找旧名字的祖先，就是新名字。

if(!id[old_name]){
    id[old_name] = ++ num;
   ans[++ cnt] = old_num;//初始名字
}
if(!id[new_name]){
    id[new_name] = ++ num;
}
f[old_name] = new_name;

Code

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<queue>
#include<map>

using namespace std;

#define db double
#define INF 0x3f3f3f3f
#define LINF 0x3f3f3f3f3f3f3f3f
#define For(i,j,k) for(int i=j;i<=k;++i)
#define endl '\n'
#define IOS ios::sync_with_stdio(0)

const int M = 2e5 + 10;

int q;
int cnt, num;
string name[M];
map<string, int> id;
map<string, string> f;//用map做father数组
string find(string x){
    if(x == f[x]) return x;
    return f[x] = find(f[x]);
}

signed main() {
    IOS;
    cin >> q;
    while(q --){
        string od, nw;
        cin >> od >> nw;
        if(id[od] == 0){
            id[od] = ++ num;
            f[od] = od;
            name[++ cnt] = od;
        }
        if(!id[nw]){
            id[nw] = ++ num;
            f[nw] = nw;
        }
        f[od] = nw;
    }
    cout << cnt << endl;
    For(i, 1, cnt){
        cout << name[i] << ' ' << find(name[i]) << endl;
    }
    return 0;
}