Tyvj P2044 ["扫地"杯III day2]旅游景点

二次联通门 : Tyvj P2044 ["扫地"杯III day2]旅游景点

/*
    Tyvj P2044 ["扫地"杯III day2]旅游景点

    并查集
    先把大于K的点合并
    再从头扫一遍
    若当前边的两边不在同一个集合就合并
    否则就割掉这条边
*/
#include <cstdio>
#include <iostream>

const int BUF = 12312313;
char Buf[BUF], *buf = Buf;

inline void read (int &now)
{
    for (now = 0; !isdigit (*buf); ++ buf);
    for (; isdigit (*buf); now = now * 10 + *buf - ‘0‘, ++ buf);
}

#define Max 100009
struct E { int u, v; };
int f[Max]; E e[Max << 1];
int Find (int x) { return f[x] == x ? x : f[x] = Find (f[x]); }

int main (int argc, char *argv[])
{
    freopen ("1.in", "r", stdin); fread (buf, 1, BUF, stdin);
    int N, M, K, x, y, Answer = 0; register int i, j;
    read (N), read (M), read (K);
    for (i = 1; i <= N; ++ i) f[i] = i;
    for (i = 1; i <= M; ++ i)
    {
        read (e[i].u), read (e[i].v);
        if (e[i].u > K && e[i].v > K)
        {
            x = Find (e[i].u), y = Find (e[i].v);
            f[x] = f[y];
        }
    }
    for (i = 1; i <= M; ++ i)
    {
        if (e[i].u > K && e[i].v > K) continue;
        x = Find (e[i].u), y = Find (e[i].v);
        if (x != y) f[x] = y;
        else ++ Answer;
    }
    printf ("%d", Answer);
    return 0;
}