最小结点覆盖,二分图最大匹配(匈牙利算法)
首先读入 双向建边,得到无向的二分图
然后匈牙利匹配,得到的答案除以2
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妈耶,,他说是树形图,我就按最小支配集做,但是死活过不了,为啥呢???
有大神路过 求指点
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <cmath>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <ctype.h>
#include <vector>
#include <algorithm>
#include <sstream>
#define PI acos(-1.0)
#define in freopen("in.txt", "r", stdin)
#define out freopen("out.txt", "w", stdout)
using namespace std;
typedef long long ll;
const int maxn = 15000+7, INF = 0x3f3f3f3f;
int n, ans;
vector<int> a[maxn];
int vis[maxn], f[maxn];
void init() {
for(int i = 0; i <= n+1; ++i)
a[i].clear();
for(int j = 0; j < n; ++j) {
int u, v, cnt;
scanf("%d:(%d)", &u, &cnt);
for(int i = 0; i < cnt; ++i) {
scanf("%d", &v);
a[u].push_back(v);
a[v].push_back(u);
}
}
memset(f, -1, sizeof f);
}
bool dfs(int id) {
for(int i = 0; i < a[id].size(); ++i) {
if(vis[a[id][i]] == 0) {
vis[a[id][i]] = 1;
if(f[a[id][i]] == -1 || dfs(f[a[id][i]])) {
f[a[id][i]] = id;
return true;
}
}
}
return false;
}
int main() {
while(scanf("%d", &n) != EOF && n) {
init();
ans = 0;
for(int i = 0; i < n; ++i) {
memset(vis, 0, sizeof vis);
if(dfs(i)) ans++;
}
printf("%d\n", ans/2);
}
return 0;
}