【线性规划与网络流 24题】完成度(1/24)

#include<queue>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define read(x) x=getint()
using namespace std;
const int N = 1003;
int getint() {
	int k = 0, fh = 1; char c = getchar();
	for(; c < ‘0‘ || c > ‘9‘; c = getchar())
		if (c == ‘-‘) fh = -1;
	for(; c >= ‘0‘ && c <= ‘9‘; c = getchar())
		k = k * 10 + c - ‘0‘;
	return k * fh;
}
queue<int> q;
bool vis[N];
int point[N], cap[N], nxt[N], to[N], d[N], cur[N], S, T, cnt = 1;
bool BFS() {
	memset(vis, 0, sizeof(vis));
	q.push(S); d[S] = 0; vis[S] = 1;
	int u, i;
	while (!q.empty()) {
		u = q.front(); q.pop();
		for(i = point[u]; i; i = nxt[i])
			if (!vis[to[i]] && cap[i]) {
				d[to[i]] = d[u] + 1;
				vis[to[i]] = 1;
				q.push(to[i]);
			}
	}
	return vis[T];
}
int DFS(int u, int a) {
	if (u == T || !a) return a;
	int f, flow = 0;
	for(int i = cur[u]; i; i = nxt[i])
		if (d[u] + 1 == d[to[i]] && (f = DFS(to[i], min(a, cap[i]))) > 0) {
			flow += f; a -= f; cap[i] -= f; cap[i ^ 1] += f;
			if (!a) break;
		}
	return flow;
}
int Dinic() {
	int flow = 0, i;
	while (BFS()) {
		for(i = 1; i <= T; ++i) cur[i] = point[i];
		flow += DFS(S, 0x7fffffff);
	}
	return flow;
}
void ins(int x, int y, int z) {
	nxt[++cnt] = point[x]; to[cnt] = y; cap[cnt] = z; point[x] = cnt;
}
void findpair(int x) {
	for(int i = point[x]; i; i = nxt[i])
		if (cap[i] == 0 && to[i] != S) {printf("%d %d\n", x, to[i]); break;}
}
int main() {
	int n, m;
	read(n); read(m);
	S = n + m + 1; T = S + 1;
	for(int i = 1; i <= n; ++i)
		ins(S, i, 1), ins(i, S, 0);
	for(int i = n + 1; i <= n + m; ++i)
		ins(i, T, 1), ins(T, i, 0);
	int u, v;
	read(u); read(v);
	while (u != -1 && v != -1) {
		ins(u, v, 1); ins(v, u, 0);
		read(u); read(v);
	}
	printf("%d\n", Dinic());
	for(int i = 1; i <= n; ++i)
		findpair(i);
	return 0;
}