有趣的事

#include <cstdio>
#define N (int(2e5 + 10))

bool vis[N];
int fa[N], n, m, p, q, ans, i, j;

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

void merge(int a, int b){
    if(Fa(a) != Fa(b)) 
        fa[Fa(a)] = Fa(b);
}

bool in(int a, int b){
    return Fa[a] == Fa[b];
}

int main(){
    scanf("%d%d", &n, &m);
    for(i = 1; i <= n; i ++)
        fa[i] = i;
    for(i = 1; i <= m; i ++)
        scanf("%d%d", &p, &q),
        merge(p, q);
    for(i = 1; i <= n; i ++)
        vis[Fa(i)] = true;
    for(i = 1; i <= n; i ++)
        ans += vis[i];
    printf("%d\n", ans);
    return 0;
}```

#include <cstdio>
#define N (int(2e5 + 10))

bool vis[N];
int fa[N], n, m, p, q, ans, i, j;

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

void merge(int a, int b){
    if(Fa(a) != Fa(b)) 
        fa[Fa(a)] = Fa(b);
}

bool in(int a, int b){
    return Fa[a] == Fa[b];
}

int main(){
    scanf("%d%d", &n, &m);
    for(i = 1; i <= n; i ++)
        fa[i] = i;
    for(i = 1; i <= m; i ++)
        scanf("%d%d", &p, &q),
        merge(p, q);
    for(i = 1; i <= n; i ++)
        vis[Fa(i)] = true;
    for(i = 1; i <= n; i ++)
        ans += vis[i];
    printf("%d\n", ans - 1); //唯一区别
    return 0;
}```