HDU4532（组合DP） n种不同的元素，相同的不能相邻

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当n为三时，写了个暴力的

#include <iostream>
#include <cstdio>
#include <map>
#include <cmath>
using namespace std;
const int N = 105;
long long dp[N][N][N][3];
int main()
{
    int a,b,c;
    cin >> a >> b >> c;
    for(int i = a;i <= a+1;i++)
        for(int j = b;j <= b+1;j++)
            for(int k = c;k <= c+1;k++)
                for(int h = 0;h < 3;h++)
                    dp[i][j][k][h] = 0;
    dp[a-1][b][c][0] = 1;
    dp[a][b-1][c][1] = 1;
    dp[a][b][c-1][2] = 1;
    for(int i = a;i >= 0;i--)
        for(int j = b;j >= 0;j--)
            for(int k = c;k >= 0;k--){


                dp[i][j][k][0] +=  dp[i+1][j][k][1] + dp[i+1][j][k][2];
                dp[i][j][k][1] += dp[i][j+1][k][0]  + dp[i][j+1][k][2];
                dp[i][j][k][2] += dp[i][j][k+1][0] + dp[i][j][k+1][1] ;

            }

    printf("%lld\n",dp[0][0][0][0]+dp[0][0][0][1]+dp[0][0][0][2]);
}

HDU4532
思路：
https://www.zhihu.com/question/29890888

https://www.douban.com/note/269136472/