zoj2771 Get Out of the Glass(DP)

/*
 简单DP：分成奇偶两种状况考虑
   奇数情况：每个面的光线等于上次的本平面以上的点的反射
   偶数情况：每个面的光线等于上次的本平面以下的点的反射
*/

#include <stdio.h>
#include <string.h>

long long F[ 61 ][ 4 ];

int main()
{
    int i,j,k,n;
    memset( F, 0L, sizeof( F ) );
    F[ 0 ][ 0 ] = 1L;
    
    for ( i = 1 ; i <= 60 ; ++ i )
    for ( j = 0 ; j <= 3  ; ++ j ) 
        if ( i%2 ) {
            for ( k =  0  ; k < j ; ++ k )
                F[ i ][ j ] += F[ i-1 ][ k ];
        }else {
            for ( k = j+1 ; k <= 3 ; ++ k )
                F[ i ][ j ] += F[ i-1 ][ k ];
        }
    while ( scanf("%d",&n) != EOF ) {
        long long sum = 0;
        for ( i = 0 ; i < 3 ; ++ i )
            sum += F[ n ][ i+n%2 ];
        printf("%lld\n",sum);
    }
    return 0;
}