poj1325

最小点集覆盖

匈牙利算法

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
using namespace std;

#define maxn 105

int n, uN, vN;
bool g[maxn][maxn];
int xM[maxn], yM[maxn];
bool chk[maxn];

bool SearchPath(int u)
{
    int v;
    for (v = 0; v < vN; v++)
        if (g[u][v] && !chk[v])
        {
            chk[v] = true;
            if (yM[v] == -1 || SearchPath(yM[v]))
            {
                yM[v] = u;
                xM[u] = v;
                return true;
            }
        }
    return false;
}

int MaxMatch()
{
    int u, ret = 0;
    memset(xM, -1, sizeof(xM));
    memset(yM, -1, sizeof(yM));
    for (u = 0; u < uN; u++)
        if (xM[u] == -1)
        {
            memset(chk, false, sizeof(chk));
            if (SearchPath(u))
                ret++;
        }
    return ret;
}

void input()
{
    scanf("%d%d", &vN, &n);
    memset(g, 0, sizeof(g));
    for (int i = 0; i < n; i++)
    {
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);
        if (b && c)
            g[b][c] = true;
    }
}

int main()
{
    //freopen("t.txt", "r", stdin);
    while (scanf("%d", &uN), uN)
    {
        input();
        int ans = MaxMatch();
        printf("%d\n", ans);
    }
    return 0;
}