hdu 3549 Flow Problem (最大流)

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>

using namespace std;

const int N = 20;
const int INF = 0x7fffffff;

int flow
;
int cap

;
int pre
;

queue<int>q;

int m, n;

int BFS(int src, int des)
{
while (!q.empty()) q.pop();
for (int i = 1; i <= n; ++i) pre[i] = -1;
flow[src] = INF;
pre[src] = 0;
q.push(src);
while (!q.empty()) {
int index = q.front();
q.pop();
if (index == des) break;
for (int i = 1; i <= n; ++i) {
if (pre[i] == -1 && cap[index][i] > 0) {
pre[i] = index;
flow[i] = min(cap[index][i], flow[index]);
q.push(i);
}
}
}
if (pre[des] == -1) return -1;
return flow[des];
}

int maxFlow(int src, int des)
{
int ans = 0;
int in = 0;
while ((in = BFS(src, des)) != -1) {
int k = des;
while (k != src) {
int last = pre[k];
cap[last][k] -= in;
cap[k][last] += in;
k = last;
}
ans += in;
}
return ans;
}

int main()
{
int t;
int i, k;
scanf("%d", &t);
for (k = 1; k <= t; ++k) {
memset(cap, 0, sizeof cap);
memset(flow, 0, sizeof flow);
scanf("%d%d", &n, &m);
for (i = 0; i < m; ++i) {
int a, b, c;
scanf("%d%d%d", &a, &b, &c);
cap[a][b] += c;
}
printf("Case %d: %d\n", k, maxFlow(1, n));
}
return 0;
}