uoj #79 一般图最大匹配 (带花树)

传送门：http://uoj.ac/problem/79

  求一般图的最大匹配。

  带花树模板题。

  模板链接：https://blog.csdn.net/Frods/article/details/54564401

AC代码：

#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cstdlib>
#include<utility>
#include<algorithm>
#include<utility>
#include<queue>
#include<vector>
#include<set>
#include<stack>
#include<cmath>
#include<map>
#include<ctime>
#define P pair<int,int>
#define ll long long
#define ull unsigned long long
#define lson id*2,l,mid
#define rson id*2+1,mid+1,r
#define ls id*2
#define rs id*2+1
#define Mod(a,b) a<b?a:a%b+b 
	using namespace std;

const ll M = 1e9 + 7;
const ll INF = 1e9;
const int N = 510;
const double e = 10e-6;

int n, m;

struct blossemtree {
	vector<int>g[N];queue<int>q;
	int fa[N], type[N], link[N], Next[N], vis[N];
	int find(int x) {
		if (x == fa[x]) return x;
		return fa[x] = find(fa[x]);
	}
	void add(int u, int v) {
		g[u].push_back(v);
	}
	void combine(int x, int lca) {
		while (x != lca) {
			int u = link[x], v = Next[u];
			if (find(v) != lca) Next[v] = u;
			if (type[u] == 1) type[u] = 2, q.push(u);
			fa[find(x)] = find(u);fa[find(u)] = find(v);
			x = v;
		}
	}
	void contrack(int x, int y) {
		int lca = x;
		memset(vis, 0, sizeof(vis));
		for (int i = x; i; i = Next[link[i]]) {
			i = find(i);
			vis[i] = 1;
		}
		for (int i = y; i; i = Next[link[i]]) {
			i = find(i);
			if (vis[i]) {
				lca = i;
				break;
			}
		}
		if (lca != find(x)) Next[x] = y; 
		if (lca != find(y)) Next[y] = x;
		combine(x, lca);combine(y, lca);
	}
	void bfs(int S) {
		memset(type, 0, sizeof(type));
		memset(Next, 0, sizeof(Next));
		for (int i = 1; i <= n; i++) 
			fa[i] = i;
		while (!q.empty()) 
			q.pop();
		q.push(S); type[S] = 2; 
		while (!q.empty()) {
			int x = q.front();q.pop();
			for (int i = 0; i < g[x].size(); i++) {
				int y = g[x][i];
				if (find(x) == find(y) || link[x] == y || type[y] == 1) continue;
				if (type[y] == 2) 
					contrack(x, y);
				else if (link[y]) {
					Next[y] = x;
					type[y] = 1;
					type[link[y]] = 2;
					q.push(link[y]);
				}
				else {
					Next[y] = x;
					int pos = y, u = Next[pos], v = link[u];
					while (pos) {
						link[pos] = u; link[u] = pos;
						pos = v;
						u = Next[pos]; v = link[u];
					}
					return;
				}
			}
		}
	}
	int maxmatch() {
		for (int i = 1; i <= n; i++)
			if (!link[i]) bfs(i);
		int ans = 0;
		for (int i = 1; i <= n; i++)
			if (link[i]) ans++;
		return ans / 2;
	}
	void init() {
		for (int i = 1; i <= n; i++) g[i].clear();
		memset(link, 0, sizeof(link));
	}
}tree;

int main() {
	int u, v;
	while (~scanf("%d%d", &n, &m)) {
		tree.init();
		while (m--) {
			scanf("%d%d", &u, &v);
			tree.add(u, v); tree.add(v, u);
		}
		printf("%d\n", tree.maxmatch());
		for (int i = 1; i <= n; i++)
			printf("%d ", tree.link[i]);
		printf("\n");
	}

	return 0;
}