300

4 5
1 2 1
2 3 1
3 4 1
1 3 2
2 4 2

6

• 最短路 = 最小费用
• 每个边一次 = 流量为1

# 代码

`cpp FJ的旅行 https://github.com/OhYee/sourcecode/tree/master/ACM 代码备份
/*/
#define debug
#include
//*/
#include
#include
#include
#include
#include
#include
#include
using namespace std;

const int MAXN = 1005;
const int MAXM = 10005;
const int INF = 0x3f3f3f3f;
struct Edge {
int to,next,cap,flow,cost;
}edge[MAXM];

int pre[MAXN],dis[MAXN];
bool vis[MAXN];
int N;//节点总个数，节点编号从0~N-1
void init(int n){
N = n;
tol = 0;
}
void addedge(int u,int v,int cap,int cost) {
edge[tol].to = v;
edge[tol].cap = cap;
edge[tol].cost = cost;
edge[tol].flow = 0;
edge[tol].to = u;
edge[tol].cap = 0;
edge[tol].cost = -cost;
edge[tol].flow = 0;
}
bool spfa(int s,int t) {
queueq;
for(int i = 0;i < N;i++) {
dis[i] = INF;
vis[i] = false;
pre[i] = -1;
}
dis[s] = 0;
vis[s] = true;
q.push(s);
while(!q.empty()){
int u = q.front();
q.pop();
vis[u] = false;
for(int i = head[u]; i != -1;i = edge[i].next){
int v = edge[i].to;
if(edge[i].cap > edge[i].flow &&
dis[v] > dis[u] + edge[i].cost ){
dis[v] = dis[u] + edge[i].cost;
pre[v] = i;
if(!vis[v]){
vis[v] = true;
q.push(v);
}
}
}
}
if(pre[t] == -1)return false;
else return true;
}
//返回的是最大流，cost存的是最小费用
int minCostMaxflow(int s,int t,int &cost) {
int flow = 0;
cost = 0;
while(spfa(s,t)){
int Min = INF;
for(int i = pre[t];i != -1;i = pre[edge[i^1].to]){
if(Min > edge[i].cap - edge[i].flow)
Min = edge[i].cap - edge[i].flow;
}
for(int i = pre[t];i != -1;i = pre[edge[i^1].to]){
edge[i].flow += Min;
edge[i^1].flow -= Min;
cost += edge[i].cost * Min;
}
flow += Min;
}
return flow;
}

int main(){
#ifdef debug
freopen("in.txt", "r", stdin);
int START = clock();
#endif
cin.tie(0);
cin.syncwithstdio(false);

int n, m;
while(cin>>n>>m){
init(n+1);
for(int i=0;iint u,v,cost;
cin >> u >> v >> cost;
}