SDOI 2006 - 保安站岗

最小点费用覆盖，即选中费用最小的i个点把所有的边覆盖。

#include <cstdio>

using namespace std;

#define MAXV    1505

#define MAXE    (MAXV - 1)

int Vefw[MAXE], Veh[MAXV], Vet[MAXE], Vc[MAXV], Veptr;

int dp[MAXV][3],dp2[MAXV];
#define min(a,b) ((a)<(b)?(a):(b))
#define addedge(s,t)    do{\

    Vefw[Veptr] = Veh[s], Vet[Veptr] = t;        Veh[s] = ++Veptr;}while(0)
void solve(int s)

{

    dp[s][2] = 0, dp[s][1] = Vc[s];

    for(int e = Veh[s]; e; e = Vefw[e]) {

        int t = Vet[--e];

        solve(t);

        dp[s][1] += min(min(dp[t][0], dp[t][1]), dp[t][2]);

        dp[s][2] += min(dp[t][0], dp[t][1]);

    }

    int k;

    dp2[k=s] = 0x3f3f3f3f;

    for(int e1 = Veh[s]; e1; e1 = Vefw[e1]) {

        int t1 = Vet[--e1];

        dp2[t1] = dp[t1][1];

        for(int e2 = Veh[s]; e2; e2 = Vefw[e2]) {

            int t2 = Vet[--e2];

            if (t2 != t1) dp2[t1] += min(dp[t2][0], dp[t2][1]);

        }

        if (dp2[k] > dp2[t1]) k = t1;

    }

    dp[s][0] = dp2[k];

}
int N;
int main(void)

{

//    freopen("sdoi2006_guard.txt", "r", stdin);

    scanf("%d", &N);

    int root = 0;

    for(int i=0; i<N; ++i) {

        int s, k, c;

        scanf("%d%d%d", &s, &k, &c);

        Vc[--s] = k;

        while(c) {

            int t;

            scanf("%d", &t); --t;

            if (t == root) root = s;

            addedge(s, t);

            --c;

        }

    }

    solve(root);

    printf("%d\n", min(dp[root][0], dp[root][1]));

    return 0;

}

SDOI 2006 - 保安站岗,布布扣,bubuko.com