POJ 3469 最小割

#include <cstdio>
#include <algorithm>
#include <vector>
#include <iostream>
#include <queue>
#include <cstring>
using namespace std;
const int INF = 0x3f3f3f3f;
const int MAX_N = 2E4 + 10;
const int MAX_M = 2E5 + 10;
int N, M, A[MAX_N], B[MAX_N], b[MAX_M], a[MAX_M], w[MAX_M];
struct Edge
{
int from, to, cap, flow;
Edge(int from, int to, int cap, int flow): from(from), to(to), cap(cap), flow(flow) {}
};

struct Dinic
{
int n, m, s, t;
vector<Edge>edges;
vector<int>G[MAX_N];
bool vis[MAX_N];
int d[MAX_N], cur[MAX_N];
void add_edge(int from, int to, int cap)
{
edges.push_back(Edge(from, to, cap, 0));
edges.push_back(Edge(to, from, 0, 0));
m = edges.size();
G[from].push_back(m - 2);
G[to].push_back(m - 1);
}
bool BFS()
{
memset(vis, 0, sizeof(vis));
queue<int>Q;
Q.push(s);
d[s] = 0;
vis[s] = 1;
while (!Q.empty())
{
int x = Q.front(); Q.pop();
for (int i = 0; i < G[x].size(); i++)
{
Edge &e  = edges[G[x][i]];
if (!vis[e.to] && e.cap > e.flow)
{
vis[e.to] = 1;
d[e.to] = d[x] + 1;
Q.push(e.to);
}
}
}
return vis[t];
}
int DFS(int x, int a)
{
if (x == t || a == 0) return a;
int flow = 0, f;
for (int &i = cur[x]; i < G[x].size(); i++)
{
Edge &e = edges[G[x][i]];
if (d[x] + 1 == d[e.to] && (f = DFS(e.to, min(a, e.cap - e.flow))) > 0)
{
e.flow += f;
edges[G[x][i] ^ 1].flow -= f;
flow += f;
a -= f;
if (a == 0) break;
}
}
return flow;
}
int max_flow(int s, int t)
{
this->s = s;
this->t = t;
int flow = 0;
while (BFS())
{
memset(cur, 0, sizeof(cur));
flow += DFS(s, INF);
}
return flow;
}
};
Dinic D;
void solve()
{
int s = N, t = s + 1;
for (int i = 0; i < N; i++)
D.add_edge(i, t, A[i]), D.add_edge(s, i, B[i]);
for (int i = 0; i < M; i++)
D.add_edge(a[i] - 1, b[i] - 1, w[i]), D.add_edge(b[i] - 1, a[i] - 1, w[i]);
printf("%d\n", D.max_flow(s, t));
}
int main(int argc, char const *argv[])
{
while (~scanf("%d%d", &N, &M) && N + M)
{
for (int i = 0; i < N; i++)
scanf("%d%d", &A[i], &B[i]);
for (int i = 0; i < M; i++)
scanf("%d%d%d", &a[i], &b[i], &w[i]);
solve();
}
return 0;
}