CCF CSP 管道清洁 无源上下界最小费用可行流

#include <iostream>
#include <cstring>
#include <algorithm>

using namespace std;
const int N = 1e5+10, M = 1e6+10, INF = 0x3f3f3f3f;
int h[N],ecnt,A[N];
struct Edge{
    int to,nxt,f, w;
}e[M];
int q[M],vis[N],dis[N], flow[N], pre[N];
int n,m,S,T,E,sum,Enum;
void add(int a,int b,int f,int w)
{
    e[ecnt].to = b, e[ecnt].f = f, e[ecnt].w = w, e[ecnt].nxt = h[a], h[a] = ecnt ++;
    e[ecnt].to = a, e[ecnt].f = 0, e[ecnt].w = -w,e[ecnt].nxt = h[b], h[b] = ecnt ++;
}
int spfa()
{
    memset(dis, 0x3f, sizeof dis);
    memset(vis, 0, sizeof vis);
    memset(pre, -1, sizeof pre);
    int hh = 0, tt = -1;
    q[++ tt] = S; dis[S] = 0; vis[S] = 1, flow[S] = INF;
    while(hh <= tt)
    {
        int u = q[hh ++]; vis[u] = 0;
        for(int i = h[u]; ~i; i = e[i].nxt)
        {
            int to = e[i].to;
            if(e[i].f && dis[to] > dis[u] + e[i].w)
            {
                dis[to] = dis[u] + e[i].w;
                pre[to] = i;
                flow[to] = min(flow[u], e[i].f);
                if(!vis[to]) vis[to] = 1, q[++ tt] = to;
            }
        }
    }
    if(pre[T] == -1) return -1;
    return flow[T];
}

int solve()
{
    int f = 0, w = 0;
    while(spfa() != -1)
    {
        f += flow[T]; w += dis[T] * flow[T];
        int x = T;
        while(x != S)
        {
            e[pre[x]]. f -= flow[T];
            e[pre[x] ^ 1]. f += flow[T];
            x = e[pre[x] ^ 1]. to;
        }
    }
    if(f != sum) return -1;
    return w + Enum;
}
int main()
{
    int cas;
    cin >> cas >> E >> E;
    while( cas -- )
    {
        sum = Enum = ecnt = 0;
        memset(h, -1, sizeof h); 
        memset(A, 0, sizeof A);
        cin >> n >> m;
        S = 0, T  = n + 1;
        for(int i = 0; i < m; ++i)
        {
            int x, y;
            char op[2];
            scanf("%d%d%s",&x, &y, op);
            if(op[0] =='A')
            {
                add(x, y, INF, E);
                A[x] --; A[y] ++;
                Enum += E;
            }
            else if(op[0] == 'B')
            {
                A[x] --; A[y] ++;
                Enum += E;
            }
            else if(op[0] == 'C')
            {
                add(x, y, INF, E);
            }
            else add(x, y, 1, E);
        }
       
        for(int i = 1; i <= n; ++i)
            if(A[i] > 0) add(S, i, A[i], 0), sum += A[i];
            else if(A[i] < 0) add(i, T, -A[i], 0);
        printf("%d\n",solve());
    }
    
}