志愿者招募 HYSBZ - 1061（公式建图费用流）

#include <iostream>
#include <cstdio>
#include <sstream>
#include <cstring>
#include <map>
#include <cctype>
#include <set>
#include <vector>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#include <bitset>
#define rap(i, a, n) for(int i=a; i<=n; i++)
#define rep(i, a, n) for(int i=a; i<n; i++)
#define lap(i, a, n) for(int i=n; i>=a; i--)
#define lep(i, a, n) for(int i=n; i>a; i--)
#define rd(a) scanf("%d", &a)
#define rlld(a) scanf("%lld", &a)
#define rc(a) scanf("%c", &a)
#define rs(a) scanf("%s", a)
#define rb(a) scanf("%lf", &a)
#define rf(a) scanf("%f", &a)
#define pd(a) printf("%d\n", a)
#define plld(a) printf("%lld\n", a)
#define pc(a) printf("%c\n", a)
#define ps(a) printf("%s\n", a)
#define MOD 2018
#define LL long long
#define ULL unsigned long long
#define Pair pair<int, int>
#define mem(a, b) memset(a, b, sizeof(a))
#define _  ios_base::sync_with_stdio(0),cin.tie(0)
//freopen("1.txt", "r", stdin);
using namespace std;
const int maxn = 1e5 + 10, INF = 0x7fffffff, LL_INF = 0x7fffffffffffffff;
int n, m, s, t;
int head[maxn], d[maxn], vis[maxn], nex[maxn], f[maxn], p[maxn], cnt;
int xu[maxn], flow, value;

struct node
{
    int u, v, w, c;
}Node[maxn];

void add_(int u, int v, int w, int c)
{
    Node[cnt].u = u;
    Node[cnt].v = v;
    Node[cnt].w = w;
    Node[cnt].c = c;
    nex[cnt] = head[u];
    head[u] = cnt++;
}

void add(int u, int v, int w, int c)
{
    add_(u, v, w, c);
    add_(v, u, -w, 0);
}

int spfa()
{
    for(int i = 0; i < maxn; i ++) d[i] = INF;
    deque<int> Q;
    mem(vis, 0);
    mem(p, -1);
    Q.push_front(s);
    d[s] = 0;
    p[s] = 0, f[s] = INF;
    while(!Q.empty())
    {
        int u = Q.front(); Q.pop_front();
        vis[u] = 0;
        for(int i = head[u];i != -1; i = nex[i])
        {
            int v = Node[i].v;
            if(Node[i].c)
            {
                if(d[v] > d[u] + Node[i].w)
                {
                    d[v] = d[u] + Node[i].w;
                    p[v] = i;
                    f[v] = min(f[u], Node[i].c);
                    if(!vis[v])
                    {
                      //  cout << v << endl;
                        if(Q.empty()) Q.push_front(v);
                        else
                        {
                            if(d[v] < d[Q.front()]) Q.push_front(v);
                            else Q.push_back(v);
                        }
                        vis[v] = 1;
                    }
                }
            }
        }
    }
    if(p[t] == -1) return 0;
    flow += f[t], value += f[t] * d[t];
   // cout << value << endl;
    for(int i = t; i != s; i = Node[p[i]].u)
    {
        Node[p[i]].c -= f[t];
        Node[p[i] ^ 1].c += f[t];
    }
    return 1;
}

void max_flow()
{
    flow = value = 0;
    while(spfa());
    pd(value);
}

void init()
{
    mem(head, -1);
    cnt = 0;
}

int main()
{
    init();
    int u, v, w;
    rd(n), rd(m);
    s = 0, t = n + 3;
    for(int i = 1; i <= n; i++)
    {
        rd(xu[i]);
    }
    for(int i = 1; i <= m; i++)
    {
        rd(u), rd(v), rd(w);
        add(u, v + 1, w, INF);
    }
    for(int i = 1; i <= n+1; i++)
    {
        int tmp = xu[i] - xu[i - 1];
        if(tmp > 0) add(s, i, 0, tmp);
        else add(i, t, 0, -tmp);
        if(i > 1) add(i, i - 1, 0, INF);
    }
    max_flow();


    return 0;
}