P2256 一中校运会之百米跑（map+并查集）

思路：首先处理名字，让字符串直接映射唯一一个数字，这就用map<string, int>即可。

　　　然后，直接用并查集

#include<iostream>
#include<map>
#include<string>
using namespace std;

const int maxn = 2e4 + 10;
map<string, int>mm;
int fa[maxn];

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

int n, m;
string name;
string xx, yy;

int main(){
    cin >> n >> m;
    for (int i = 1; i <= n; ++i)fa[i] = i;
    for (int i = 1; i <= n; ++i)
    {
        cin >> name; mm[name] = i;
    }
    for (int i = 1; i <= m; ++i)
    {
        cin >> xx >> yy;
        int x = find(mm[xx]);
        int y = find(mm[yy]);
        if (x != y){ fa[x] = y; }
    }
    cin >> n;
    for (int i = 0; i < n; ++i)
    {
        cin >> xx >> yy;;
        int x = find(mm[xx]);
        int y = find(mm[yy]);
        if (x == y)cout << "Yes." << endl;
        else cout << "No." << endl;
    }
}