POJ 1149 PIGS

POJ_1149

I am confused about this question. Let's take a look at this blog.

Http://imlazy.ycool.com/post.2059102.html

#include<stdio.h>
#include<string.h>
#define MAXD 110
#define MAXM 30010
#define MAXm 1010
#define INF 10000000
int N, M, S, T, e, first[MAXD], work[MAXD], next[MAXM], v[MAXM], flow[MAXM], d[MAXD], q[MAXD];
int g[MAXD][MAXD], pre[MAXm], cow[MAXm];
void add(int x, int y, int z)
{
    v[e] = y;
    flow[e] = z;
    next[e] = first[x];
    first[x] = e;
    e ++;
}
void init()
{
int i, j, k, n;
    e = 0;
    S = 0, T = N + 1;
    memset(first, -1, sizeof(first));
    memset(g, 0, sizeof(g));
    memset(pre, 0, sizeof(pre));
for(i = 1; i <= M; i ++)
        scanf("%d", &cow[i]);
for(i = 1; i <= N; i ++)
    {
        scanf("%d", &n);
for(j = 0; j < n; j ++)
        {
            scanf("%d", &k);
if(k > M)
continue;
if(!pre[k])
                g[0][i] += cow[k];
else
                g[pre[k]][i] = 1;
            pre[k] = i;
        }
        scanf("%d", &k);
        add(i, T, k);
        add(T, i, 0);
    }
for(i = 1; i <= N; i ++)
if(g[0][i])
        {
            add(0, i, g[0][i]);
            add(i, 0, 0);
        }
for(i = 1; i <= N; i ++)
for(j = i + 1; j <= N; j ++)
if(g[i][j])
            {
                add(i, j, INF);
                add(j, i, 0);
            }
}
int bfs()
{
int i, j, k, rear = 0;
    memset(d, -1, sizeof(d));
    d[S] = 0;
    q[rear ++] = S;
for(i = 0; i < rear; i ++)
for(j = first[q[i]]; j != -1; j = next[j])
if(flow[j] > 0 && d[v[j]] == -1)
            {
                d[v[j]] = d[q[i]] + 1;
if(v[j] == T)
return 1;
                q[rear ++] = v[j];
            }
return 0;
}
int dfs(int cur, int a)
{
if(cur == T)
return a;
for(int &i = work[cur]; i != -1; i = next[i])
if(flow[i] > 0 && d[v[i]] == d[cur] + 1)
if(int t = dfs(v[i], a < flow[i] ? a : flow[i]))
            {
                flow[i] -= t;
                flow[i ^ 1] += t;
return t;
            }
return 0;
}
void solve()
{
int i, j, k, t, cnt = 0;
while(bfs())
    {
        memcpy(work, first, sizeof(first));
while(t = dfs(S, INF))
            cnt += t;
    }
    printf("%d\n", cnt);
}
int main()
{
while(scanf("%d%d", &M, &N) == 2)
    {
        init();
        solve();
    }
return 0;
}