HRBUST - 1490 咒語（）

並查集

#include <algorithm>
#include <cstdio>
#include <iostream>

using namespace std;

int pre[MAX];
void init(){
    for (int i = 0; i < MAX; i++)
        pre[i] = i;
}
int findx(int x){
    return x == pre[x] ? x : pre[x] = findx(pre[x]);
}
void join(int x, int y){
    int a = findx(x);
    int b = findx(y);
    if (a != b)
        pre[b] = a;
}
int main(void){
    int n;
    while (scanf("%d", &n) == 1) {
        char str[51];
        init();
        for (int i = 0; i < n; i++) {
            scanf("%s", str);
            join(str[0] - 'a', str[len - 1] - 'a');
        }
            printf("Yes\n");
        else
            printf("No\n");
    }
    return 0;
}