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  • Solution -「多校联训」数学考试

    (mathcal{Description})

      Link.

      给定 (n) 个函数,第 (i) 个有 (f_i(x)=a_ix^3+b_ix^2+cx_i+d~(xin[l_i,r_i]capmathbb Z)),还有 (m) 条形如 (x_ule x_v+d) 的限制,请最大化 (sum_{i=1}^nf_i(x_i)) 或声明无解。

      (n,|l_i|,|r_i|le 100)

    (mathcal{Solution})

      很久没遇到了,压根儿没往网络流方面想 qwq。

      对于每个 (f_i),拉一条代表 (f_i(l_i..r_i)) 的链,边权就是某个 (f) 的值的相反数;限制条件方便转化为最小割,之后直接跑最小割即可。

      (mathcal O(operatorname{Dinic}(sum(r-l),msum(r-l))))

    (mathcal{Code})

    /*~Rainybunny~*/
    
    #include <queue>
    #include <cstdio>
    
    #define rep( i, l, r ) for ( int i = l, rep##i = r; i <= rep##i; ++i )
    #define per( i, r, l ) for ( int i = r, per##i = l; i >= per##i; --i )
    
    #define int long long
    
    inline int imin( const int a, const int b ) { return a < b ? a : b; }
    
    const int MAXN = 100, IINF = 1ll << 50, BASE = 7e6;
    int n, m, lid[MAXN + 5];
    
    struct Function {
        int a, b, c, d, l, r;
        inline void read() {
            scanf( "%lld %lld %lld %lld %lld %lld" , &a, &b, &c, &d, &l, &r );
        }
        inline int operator () ( const int x ) const {
            return d + x * ( c + x * ( b + x * a ) );
        } 
    } fc[MAXN + 5];
    
    struct FlowGraph {
        static const int MAXND = 2e4 + 10, MAXEG = 2e5;
        int ecnt, bound, S, T, head[MAXND];
        struct Edge { int to, flw, nxt; } graph[MAXEG * 2];
        int ds[MAXND], curh[MAXND];
    
        FlowGraph(): ecnt( 1 ) {}
    
        inline void clear() {
            ecnt = 1;
            rep ( i, 0, bound ) head[i] = 0;
        }
    
        inline void operator () ( const int s, const int t, const int f ) {
            graph[++ecnt] = { t, f, head[s] }, head[s] = ecnt;
            graph[++ecnt] = { s, 0, head[t] }, head[t] = ecnt;
        }
    
        inline bool bfs() {
            static std::queue<int> que;
            rep ( i, 0, bound ) ds[i] = IINF;
            que.push( S ), ds[S] = 0;
            while ( !que.empty() ) {
                int u = que.front(); que.pop();
                for ( int i = head[u], v; i; i = graph[i].nxt ) {
                    if ( graph[i].flw && ds[u] + 1 < ds[v = graph[i].to] ) {
                        ds[v] = ds[u] + 1, que.push( v );
                    }
                }
            }
            return ds[T] != IINF;
        }
    
        inline int dfs( const int u, int iflw ) {
            if ( u == T ) return iflw;
            int oflw = 0;
            for ( int& i = curh[u], v; i; i = graph[i].nxt ) {
                if ( graph[i].flw && ds[u] + 1 == ds[v = graph[i].to] ) {
                    int tmp = dfs( v, imin( iflw - oflw, graph[i].flw ) );
                    oflw += tmp, graph[i].flw -= tmp, graph[i ^ 1].flw += tmp;
                    if ( iflw == oflw ) break;
                }
            }
            if ( !oflw ) ds[u] = IINF;
            return oflw;
        }
    
        inline int calc( const int s, const int t ) {
            int ret = 0; S = s, T = t;
            while ( bfs() ) {
                rep ( i, 0, bound ) curh[i] = head[i];
                ret += dfs( S, IINF );
            }
            return ret;
        }
    } G;
    
    signed main() {
        freopen( "sleep.in", "r", stdin );
        freopen( "sleep.out", "w", stdout );
    
        int Q; scanf( "%lld", &Q );
        while ( Q-- ) {
            scanf( "%lld %lld", &n, &m ), G.clear();
            int S = 0, T = 1, node = 1;
            rep ( i, 1, n ) {
                fc[i].read();
                G( S, lid[i] = ++node, IINF );
                rep ( j, fc[i].l, fc[i].r ) {
                    G( node, node + 1, BASE - fc[i]( j ) ), ++node;
                }
                G( node, T, IINF );
            }
            rep ( i, 1, m ) {
                int u, v, d; scanf( "%lld %lld %lld", &u, &v, &d );
                rep ( x, fc[u].l, fc[u].r ) {
                    if ( fc[v].l <= x - d && x - d <= fc[v].r ) {
                        G( lid[u] + x - fc[u].l, lid[v] + x - d - fc[v].l, IINF );
                    } else if ( x - d > fc[v].r ) {
                        G( lid[u] + x - fc[u].l, T, IINF );
                    }
                }
            }
            G.bound = node;
            int ans = -G.calc( S, T );
            if ( ans <= -IINF ) puts( "mei ji ge" );
            else printf( "%lld
    ", ans + n * BASE );
        }
        return 0;
    }
    
    
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  • 原文地址:https://www.cnblogs.com/rainybunny/p/14999423.html
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