洛谷P3381 最小费用最大流

费用流板子

还是一道板子题。。先练练手

#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
#define full(a, b) memset(a, b, sizeof a)
using namespace std;
typedef long long ll;
inline int lowbit(int x){ return x & (-x); }
inline int read(){
    int X = 0, w = 0; char ch = 0;
    while(!isdigit(ch)) { w |= ch == '-'; ch = getchar(); }
    while(isdigit(ch)) X = (X << 3) + (X << 1) + (ch ^ 48), ch = getchar();
    return w ? -X : X;
}
inline int gcd(int a, int b){ return a % b ? gcd(b, a % b) : b; }
inline int lcm(int a, int b){ return a / gcd(a, b) * b; }
template<typename T>
inline T max(T x, T y, T z){ return max(max(x, y), z); }
template<typename T>
inline T min(T x, T y, T z){ return min(min(x, y), z); }
template<typename A, typename B, typename C>
inline A fpow(A x, B p, C lyd){
    A ans = 1;
    for(; p; p >>= 1, x = 1LL * x * x % lyd)if(p & 1)ans = 1LL * x * ans % lyd;
    return ans;
}
const int N = 5005;
const int M = 50005;
int n, m, s, t, head[N], cnt, inq[N], pre[N], incf[N], dist[N], ans, mf;
struct Edge { int v, next, f, cost; } edge[M<<1];

void addEdge(int a, int b, int f, int cost){
    edge[cnt].v = b, edge[cnt].f = f, edge[cnt].cost = cost, edge[cnt].next = head[a], head[a] = cnt ++;
    edge[cnt].v = a, edge[cnt].f = 0, edge[cnt].cost = -cost, edge[cnt].next = head[b], head[b] = cnt ++;
}

bool spfa(){
    full(dist, INF), full(inq, false);
    full(pre, 0), full(incf, INF);
    queue<int> q;
    q.push(s);
    dist[s] = 0, inq[s] = true;
    while(!q.empty()){
        int cur = q.front(); q.pop();
        inq[cur] = false;
        for(int i = head[cur]; i != -1; i = edge[i].next){
            int u = edge[i].v;
            if(edge[i].f > 0 && dist[u] > dist[cur] + edge[i].cost){
                dist[u] = dist[cur] + edge[i].cost;
                pre[u] = i, incf[u] = min(incf[cur], edge[i].f);
                if(!inq[u]) q.push(u), inq[u] = true;
            }
        }
    }
    return dist[t] != INF;
}

void mcmf(){
    while(spfa()){
        int cur = t;
        while(cur != s){
            int i = pre[cur];
            edge[i].f -= incf[t], edge[i^1].f += incf[t];
            cur = edge[i^1].v;
        }
        mf += incf[t];
        ans += dist[t] * incf[t];
    }
}

int main(){

    full(head, -1), cnt = 2;
    n = read(), m = read(), s = read(), t = read();
    for(int i = 0; i < m; i ++){
        int u = read(), v = read(), w = read(), c = read();
        addEdge(u, v, w, c);
    }
    mcmf();
    printf("%d %d\n", mf, ans);
    return 0;
}