【HDOJ】3560 Graph’s Cycle Component

并查集的路径压缩。

#include <stdio.h>
#include <string.h>

#define MAXNUM 100005

int deg[MAXNUM], bin[MAXNUM];
char isCycle[MAXNUM];

int find(int x) {
    int r = x;
    int i = x, j;

    while (r != bin[r])
        r = bin[r];

    while (i != r) {
        j = bin[i];
        bin[i] = r;
        i = j;
    }

    return r;
}

void merge(int x, int y) {
    int fx;
    int fy;

    fx = find(x);
    fy = find(y);
    if (fx != fy)
        bin[fx] = fy;
}

int main() {
    int n, m;
    int i, x, y;

    while (scanf("%d %d", &n, &m)!=EOF && (n||m)) {
        for (i=0; i<n; ++i)
            bin[i] = i;
        memset(isCycle, 0, sizeof(isCycle));
        memset(deg, 0, sizeof(deg));
        while (m--) {
            scanf("%d %d", &x, &y);
            deg[x]++;
            deg[y]++;
            merge(x, y);
        }
        m = 0;
        for (i=0; i<n; ++i) {
            x = find(i);
            if (isCycle[x] == 0) {
                ++m;
                isCycle[x] = 1;
            }
        }
        for (i=0; i<n; ++i)
            if (deg[i] != 2)
                isCycle[bin[i]] = 0;
        x = 0;
        for (i=0; i<n; ++i)
            if (isCycle[i])
                ++x;
        printf("%d %d
", m, x);
    }

    return 0;
}