CF922E Birds 题解

合集 - 题解(97)

1.BZOJ3364 Distance Queries 距离咨询 题解2023-08-082.UVA12390 Distributing Ballot Boxes 题解2023-08-243.UVA1108 Mining Your Own Business 题解2023-08-244.CF1425F Flamingoes of Mystery 题解2023-09-295.SP16113 SUBTLEBA - Trucks Transportation 题解2023-10-016.UVA12655 Trucks 题解2023-10-017.P5943 [POI2002] 最大的园地 题解2023-10-018.SP9494 ZSUM - Just Add It 题解2023-10-029.CF1878C Vasilije in Cacak 题解2023-10-0210.CF1010C Border 题解2023-10-0611.CF131D Subway 题解2023-10-0612.B3610 [图论与代数结构 801] 无向图的块 题解2023-11-0413.P9801 [NERC2018] King Kog’s Reception2023-11-0514.CF1089K King Kog's Reception 题解2023-11-0515.SP28304 ADATEAMS - Ada and Teams 题解2023-11-1916.CF327C Magic Five 题解2023-12-1617.P1405 苦恼的小明 题解2023-12-1618.SP10050 POWTOW - Power Tower City 题解2023-12-1619.SP21690 POWERUP - Power the Power Up 题解2023-12-1620.P2898 [USACO08JAN] Haybale Guessing G 题解2023-12-3121.AT_arc125_c [ARC125C] LIS to Original Sequence 题解2024-01-1322.CF1433E Two Round Dances 题解2024-01-2723.CF739A Alyona and mex 题解2024-01-2724.AT_abc270_g [ABC270G] Sequence in mod P 题解2024-02-0725.SP277 CTGAME - City Game 题解2024-02-0726.P8670 [蓝桥杯 2018 国 B] 矩阵求和 题解2024-02-1027.UVA12467 Secret Word 题解2024-02-1328.SP34020 ADAPET - Ada and Pet 题解2024-02-1329.AT_joig2021_d 展覧会 2 (Exhibition 2) 题解2024-03-0330.AT_abc184_f [ABC184F] Programming Contest 题解2024-03-0331.AT_abc343_g [ABC343G] Compress Strings 题解2024-03-1332.CF494C Helping People 题解2024-03-23

33.CF922E Birds 题解2024-03-23

34.CF1628D1 Game on Sum (Easy Version) 题解2024-03-2335.P7137 [THUPC2021 初赛] 切切糕 题解2024-03-2736.CF1392H ZS Shuffles Cards 题解2024-03-2837.luogu P1543 [POI2004] SZP 题解2024-03-3038.SP64 PERMUT1 - Permutations 题解2024-04-0739.AT_s8pc_2_e 部分文字列 题解2024-04-0740.UVA1223 Editor 题解2024-04-0741.UVA10870 Recurrences 题解2024-05-0242.UVA1362 Exploring Pyramids 题解2024-05-0243.CF1141E Superhero Battle 题解2024-05-2644.SP14943 DRTREE - Dynamically-Rooted Tree 题解2024-05-2645.UVA11922 Permutation Transformer 题解2024-05-2646.UVA1674 闪电的能量 Lightning Energy Report 题解2024-05-2647.P10499 开关问题 题解2024-06-0848.P10466 邻值查找 题解2024-06-0849.P10596 BZOJ2839 集合计数 题解2024-06-2450.UVA12369 Cards 题解2024-06-2851.CF696B Puzzles 题解2024-06-2852.P10672 【MX-S1-T1】壁垒 题解2024-06-2953.P10673 【MX-S1-T2】催化剂 题解2024-06-2954.UVA11181 条件概率 Probability|Given 题解2024-06-2955.SP8177 JZPEXT - Beautiful numbers EXTREME 题解2024-07-0256.AT_tdpc_number 数 题解2024-07-0257.AT_dp_y Grid 2 题解2024-07-0358.P7690 [CEOI2002] A decorative fence 题解2024-07-0459.SP15620 POSTERIN - Postering 题解2024-07-0460.SP14887 GOODA - Good Travels 题解2024-07-1461.P2188 小Z的 k 紧凑数 题解2024-07-1462.SP8099 TABLE - Crash´s number table 题解2024-07-3063.AT_abl_e Replace Digits 题解2024-08-0564.AT_past202010_m 筆塗り 题解2024-08-0965.P8575 「DTOI-2」星之河 题解2024-08-0966.CF641E Little Artem and Time Machine 题解2024-08-0967.P10633 BZOJ2989 数列/BZOJ4170 极光 题解2024-08-1568.P10238 [yLCPC2024] F. PANDORA PARADOXXX 题解2024-08-1669.P4271 [USACO18FEB] New Barns P 题解2024-08-1670.P8512 [Ynoi Easy Round 2021] TEST_152 题解2024-08-1871.CF1514D Cut and Stick 题解2024-08-2372.P10933 创世纪 题解2024-08-2473.P10957 环路运输 题解2024-08-2474.SP10502 VIDEO - Video game combos 题解2024-08-2575.P10956 金字塔 题解2024-08-2676.CF704B Ant Man 题解2024-09-0577.P6638 「JYLOI Round 1」常规 题解2024-09-0678.SP1825 FTOUR2 - Free tour II 题解2024-09-2379.P10603 BZOJ4372 烁烁的游戏 题解2024-09-2780.P3364 Cool loves touli 题解2024-09-3081.CF946G Almost Increasing Array 题解2024-10-0582.AT_abc283_g [ABC283G] Partial Xor Enumeration 题解2024-10-1083.CF959F Mahmoud and Ehab and yet another xor task 题解2024-10-1084.P3794 签到题IV 题解2024-10-1685.P7984 [USACO21DEC] Tickets P 题解2024-11-0886.P5479 [BJOI2015] 隐身术 题解2024-11-0887.CF2030D QED's Favorite Permutation 题解2024-11-1088.CF633H Fibonacci-ish II 题解2024-11-1489.AT_abc129_f [ABC129F] Takahashi's Basics in Education and Learning 题解2024-12-1890.P8060 [POI2003] Sums 题解2024-12-2191.AT_keyence2019_e Connecting Cities 题解2024-12-2392.CF1534G A New Beginning 题解2024-12-2693.AT_abc237_g [ABC237G] Range Sort Query 题解2024-12-3094.CF601E A Museum Robbery 题解01-0195.P5680 [GZOI2017] 共享单车 题解01-0496.P3081 [USACO13MAR] Hill Walk G 题解01-0697.AT_abc248_h [ABC248Ex] Beautiful Subsequences 题解01-10

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题目传送门

前置知识

背包 DP

解法

观察到 $w$ 极大，若使用正常的背包空间会爆炸。

依据 AT_dp_e Knapsack 2 的经验，考虑将背包“反”着用。设 $f_{i,j}$ 表示到第 $i$ 棵树时一共召唤了 $j$ 只小鸟时剩余的最大魔力值，状态转移方程为 $f_{i,j}=min(\underset{k=0}{\overset{min(j,c_i)}{max}}\{f_{i-1,j-k}-cos{t}_i\times k+x\},w+b\times j)$，边界为 $f_{0,0}=w$。

最终，有 $\underset{i=0}{\overset{\sum _{j=1}^n{c}_j}{max}}\{[f_{n,i}\ge 0]\times i\}$ 即为所求。

代码

#include<bits/stdc++.h>
using namespace std;
#define ll long long 
#define ull unsigned long long
#define sort stable_sort 
#define endl '\n'
ll c[10010],sum[10010],cost[10010],f[1010][10010];
int main()
{
    ll n,w,b,x,ans=0,i,j,k;
    cin>>n>>w>>b>>x;
    for(i=1;i<=n;i++)
    {
        cin>>c[i];
        sum[i]=sum[i-1]+c[i];
    }
    for(i=1;i<=n;i++)
    {
        cin>>cost[i];
    }
    memset(f,-0x3f,sizeof(f));
    f[0][0]=w;
    for(i=1;i<=n;i++)
    {
        for(j=0;j<=sum[i];j++)
        {
            for(k=0;k<=min(j,c[i]);k++)
            {
                if(f[i-1][j-k]-cost[i]*k>=0)
                {
                    f[i][j]=max(f[i][j],f[i-1][j-k]-cost[i]*k+x);
                }
            }
            f[i][j]=min(f[i][j],w+b*j);
        }
    }
    for(i=sum[n];i>=0;i--)
    {
        if(f[n][i]>=0)
        {
            ans=i;
            break;
        }
    }
    cout<<ans<<endl;
    return 0;
}