一道数学题.c

#include <stdio.h>

#define N 5
#define M 4

int main()
{
    int dp[N + 1][M + 1] = {{0}};
    
    dp[0][1] = 1;

    int i, j, k;
    for (i = 0; i < N; i++)
    {
        for (j = 1; j <= M; j++)
        {
            for (k = 1; k <= M; k++)
            {
                if (k != j)
                    dp[i + 1][j] += dp[i][k];
            }
        }
    }
    
    printf("%d\n", dp[N][1]);
    
    return 0;
}