[暴力DFS] [洛谷] P1057 传球游戏

数据范围较小

可以dfs

但是超时

然后暴力打表 半个小时就跑完了

O(1) AC

#include <iostream>
using namespace std;

typedef long long ll;

const int MAXN = 31;

ll arr[MAXN][MAXN] = 
{
{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
{0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0},
{0,0,2,2,6,10,22,42,86,170,342,682,1366,2730,5462,10922,21846,43690,87382,174762,349526,699050,1398102,2796202,5592406,11184810,22369622,44739242,89478486,178956970,357913942},
{0,0,2,0,8,0,32,0,128,0,512,0,2048,0,8192,0,32768,0,131072,0,524288,0,2097152,0,8388608,0,33554432,0,134217728,0,536870912},
{0,0,2,0,6,2,20,14,70,72,254,330,948,1430,3614,6008,13990,24786,54740,101118,215766,409640,854702,1652090,3396916,6643782,13530350,26667864,53971350,106914242,215492564},
{0,0,2,0,6,0,22,0,86,0,342,0,1366,0,5462,0,21846,0,87382,0,349526,0,1398102,0,5592406,0,22369622,0,89478486,0,357913942},
{0,0,2,0,6,0,20,2,70,18,252,110,924,572,3434,2730,12902,12376,48926,54264,187036,232562,720062,980674,2789164,4086550,10861060,16878420,42484682,69242082,166823430},
{0,0,2,0,6,0,20,0,72,0,272,0,1056,0,4160,0,16512,0,65792,0,262656,0,1049600,0,4196352,0,16781312,0,67117056,0,268451840},
{0,0,2,0,6,0,20,0,70,2,252,22,924,156,3432,910,12870,4760,48622,23256,184796,108528,705894,490314,2708204,2163150,10430500,9373652,40313160,40060078,156305070},
{0,0,2,0,6,0,20,0,70,0,254,0,948,0,3614,0,13990,0,54740,0,215766,0,854702,0,3396916,0,13530350,0,53971350,0,215492564},
{0,0,2,0,6,0,20,0,70,0,252,2,924,26,3432,210,12870,1360,48620,7752,184756,40698,705434,201894,2704204,961400,10401250,4440150,40123152,20030010,155172330},
{0,0,2,0,6,0,20,0,70,0,252,0,926,0,3460,0,13110,0,50252,0,194446,0,758100,0,2973350,0,11716252,0,46333566,0,183739940},
{0,0,2,0,6,0,20,0,70,0,252,0,924,2,3432,30,12870,272,48620,1938,184756,11970,705432,67298,2704156,354200,10400602,1776060,40116656,8584290,155118390},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3434,0,12902,0,48926,0,187036,0,720062,0,2789164,0,10861060,0,42484682,0,166823430},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,2,12870,34,48620,342,184756,2660,705432,17710,2704156,106260,10400600,592020,40116600,3121560,155117522},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12872,0,48656,0,185136,0,708512,0,2725408,0,10532160,0,40870080,0,159189120},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,2,48620,38,184756,420,705432,3542,2704156,25300,10400600,161460,40116600,950040,155117520},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48622,0,184796,0,705894,0,2708204,0,10430500,0,40313160,0,156305070},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,2,184756,42,705432,506,2704156,4600,10400600,35100,40116600,237510,155117520},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184758,0,705476,0,2704708,0,10405800,0,40157550,0,155402532},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,2,705432,46,2704156,600,10400600,5850,40116600,47502,155117520},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,0,705434,0,2704204,0,10401250,0,40123152,0,155172330},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,0,705432,2,2704156,50,10400600,702,40116600,7308,155117520},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,0,705432,0,2704158,0,10400652,0,40117356,0,155125640},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,0,705432,0,2704156,2,10400600,54,40116600,812,155117520},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,0,705432,0,2704156,0,10400602,0,40116656,0,155118390},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,0,705432,0,2704156,0,10400600,2,40116600,58,155117520},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,0,705432,0,2704156,0,10400600,0,40116602,0,155117580},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,0,705432,0,2704156,0,10400600,0,40116600,2,155117520},
{0,0,2,0,6,0,20,0,70,0,252,0,924,0,3432,0,12870,0,48620,0,184756,0,705432,0,2704156,0,10400600,0,40116600,0,155117522}
};

ll n, m, ans = 0;

void dfs(int rits, int step)
{
    if(step == m)
    {
        if(rits == 1)
            ans ++;

        return ;
    }
    else
    {
        dfs(rits == n ? 1 : rits + 1, step + 1);

        dfs(rits == 1 ? n : rits - 1, step + 1);
    }

}

int main()
{


    cin>>n>>m;
    
    /*for(int i = 3; i <= 30; i++)
    {
        for(int j = 1; j <= 30; j++)
        {
            cout<<i<<j<<endl;

            n = i;

            m = j;

            ans = 0;

            dfs(1, 0);

            arr[i][j] = ans;
        }
    }

    for(int i = 0; i <= 30; i++)
    {
        for(int j = 0; j <= 30; j++)
        {
            cout<<arr[i][j]<<',';
        }
        cout<<endl;
    }*/
    
    //cout<<ans<<endl;

    //dfs(1, 0);

    //cout<<ans<<endl;

    cout<<arr[n][m]<<endl;

    return 0;
}

暴力