HDU 3435 KM A new Graph Game

和HDU 3488一样的，只不过要判断一下是否有解。

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <vector>
using namespace std;

const int maxn = 1000 + 10;
const int INF = 0x3f3f3f3f;

int n, m;

int W[maxn][maxn], lft[maxn];
int slack[maxn];
int Lx[maxn], Ly[maxn];
bool S[maxn], T[maxn];

bool match(int u)
{
    S[u] = true;
    for(int v = 1; v <= n; v++) if(!T[v])
    {
        int t = Lx[u] + Ly[v] - W[u][v];
        if(0 == t)
        {
            T[v] = true;
            if(!lft[v] || match(lft[v]))
            {
                lft[v] = u;
                return true;
            }
        }
        else slack[v] = min(slack[v], t);
    }

    return false;
}

void update()
{
    int a = INF;
    for(int i = 1; i <= n; i++) if(!T[i]) a =  min(a, slack[i]);
    for(int i = 1; i <= n; i++)
    {
        if(S[i]) Lx[i] -= a;

        if(T[i]) Ly[i] += a;
        else  slack[i] -= a;
    }
}

void KM()
{
    memset(Ly, 0, sizeof(Ly));
    memset(lft, 0, sizeof(lft));
    for(int i = 1; i <= n; i++) Lx[i] = -INF;
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++) Lx[i] = max(Lx[i], W[i][j]);

    for(int i = 1; i <= n; i++)
    {
        memset(slack, 0x3f, sizeof(slack));
        for(;;)
        {
            memset(S, false, sizeof(S));
            memset(T, false, sizeof(T));
            if(match(i)) break;
            update();
        }
    }
}

int main()
{
    int T; scanf("%d", &T);
    for(int kase = 1; kase <= T; kase++)
    {
        scanf("%d%d", &n, &m);
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= n; j++)
                W[i][j] = -INF;
        for(int i = 0; i < m; i++)
        {
            int u, v, d; scanf("%d%d%d", &u, &v, &d);
            if(W[u][v] < -d) W[u][v] = W[v][u] = -d;
        }

        KM();

        bool ok = true;
        int ans = 0;
        for(int i = 1; i <= n; i++)
        {
            if(W[lft[i]][i] == -INF) { ok = false; break; }
            ans += W[lft[i]][i];
        }
        printf("Case %d: ", kase);
        if(!ok) puts("NO");
        else printf("%d
", -ans);
    }

    return 0;
}