OJ-Problems-Source/HDOJ/2121_autoAC.cpp

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#include<iostream>
using namespace std;
#include<cstdio>
#include<cstring>
#define MAXN 1005
#define INF 0x7f7f7f7f
typedef __int64 type;
struct node
{
int u, v;
type w;
}edge[MAXN * MAXN];
int pre[MAXN], id[MAXN], vis[MAXN], n, m, pos;
type in[MAXN];
type Directed_MST(int root, int V, int E)
{
type ret = 0;
while(true)
{
int i;
for( i = 0; i < V; i++)
in[i] = INF;
for( i = 0; i < E; i++)
{
int u = edge[i].u;
int v = edge[i].v;
if(edge[i].w < in[v] && u != v)
{
pre[v] = u;
in[v] = edge[i].w;
if(u == root)
pos = i;
}
}
for( i = 0; i < V; i++)
{
if(i == root)
continue;
if(in[i] == INF)
return -1;
}
int cnt = 0;
memset(id, -1, sizeof(id));
memset(vis, -1, sizeof(vis));
in[root] = 0;
for( i = 0; i < V; i++)
{
ret += in[i];
int v = i;
while(vis[v] != i && id[v] == -1 && v != root)
{
vis[v] = i;
v = pre[v];
}
if(v != root && id[v] == -1)
{
for(int u = pre[v]; u != v; u = pre[u])
id[u] = cnt;
id[v] = cnt++;
}
}
if(cnt == 0)
break;
for( i = 0; i < V; i++)
if(id[i] == -1)
id[i] = cnt++;
for( i = 0; i < E; i++)
{
int u = edge[i].u;
int v = edge[i].v;
edge[i].u = id[u];
edge[i].v = id[v];
if(id[u] != id[v])
edge[i].w -= in[v];
}
V = cnt;
root = id[root];
}
return ret;
}
int main()
{
int i;
while(scanf("%d%d", &n, &m) != EOF)
{
type sum = 0;
for( i = 0; i < m; i++)
{
scanf("%d%d%I64d", &edge[i].u, &edge[i].v, &edge[i].w);
edge[i].u++; edge[i].v++;
sum += edge[i].w;
}
sum ++;
for( i = m; i < m + n; i++)
{
edge[i].u = 0;
edge[i].v = i - m + 1;
edge[i].w = sum;
}
type ans = Directed_MST(0, n + 1, m + n);
if(ans == -1 || ans - sum >= sum)
puts("impossible");
else
printf("%I64d %d\n",ans - sum, pos - m);
puts("");
}
return 0;
}