You cannot select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
64 lines
1.8 KiB
C++
64 lines
1.8 KiB
C++
#include <cstdio>
|
|
#include <cstring>
|
|
inline int min(int a, int b) { return a < b ? a : b; }
|
|
const int inf = 0x3f3f3f3f, N = 1005, M = 50005;
|
|
int adj[N], nxt[M], to[M], cap[M], cost[M], dis[N], ecnt, idx;
|
|
inline void addEdge_impl_(int f, int t, int c, int w)
|
|
{
|
|
nxt[ecnt] = adj[f];
|
|
adj[f] = ecnt;
|
|
to[ecnt] = t;
|
|
cap[ecnt] = c;
|
|
cost[ecnt] = w;
|
|
ecnt++;
|
|
}
|
|
inline void addEdge(int f, int t, int c, int w)
|
|
{
|
|
addEdge_impl_(f, t, c, w);
|
|
addEdge_impl_(t, f, 0, -w);
|
|
}
|
|
int T;
|
|
bool bfs(int S)
|
|
{
|
|
memset(dis, inf, sizeof(dis)), idx++;
|
|
static int que[N << 1];
|
|
static bool inq[N];
|
|
int len = 0;
|
|
dis[que[len++] = S] = 0;
|
|
for (int i = 0; i < len; inq[que[i++]] = false)
|
|
for (int e = adj[que[i]]; ~e; e = nxt[e])
|
|
if (cap[e] && dis[to[e]] > dis[que[i]] + cost[e])
|
|
{
|
|
dis[to[e]] = dis[que[i]] + cost[e];
|
|
if (!inq[to[e]]) que[len++] = to[e];
|
|
}
|
|
return dis[T] < inf;
|
|
}
|
|
int dfs(int x, int rest)
|
|
{
|
|
static int vis[N];
|
|
if (x == T) return rest;
|
|
vis[x] = idx;
|
|
int flow = 0;
|
|
for (int e = adj[x], curFlow; rest && ~e; e = nxt[e])
|
|
if (vis[to[e]] != idx && cap[e] && dis[to[e]] == dis[x] + cost[e])
|
|
if (bool(curFlow = dfs(to[e], min(cap[e], rest))))
|
|
rest -= curFlow, flow += curFlow, cap[e] -= curFlow,
|
|
cap[e ^ 1] += curFlow;
|
|
return flow;
|
|
}
|
|
int main()
|
|
{
|
|
memset(adj, -1, sizeof(adj));
|
|
int n, m;
|
|
scanf("%d%d", &n, &m);
|
|
T = n + 1;
|
|
for (int i = 0, x, y, z; i < m; i++)
|
|
scanf("%d%d%d", &x, &y, &z), addEdge(x, y, 1, z), addEdge(y, x, 1, z);
|
|
addEdge(0, 1, 2, 0);
|
|
addEdge(n, T, 2, 0);
|
|
int ans = 0;
|
|
while (bfs(0)) ans += dis[T] * dfs(0, inf);
|
|
printf("%d", ans);
|
|
return 0;
|
|
} |