Ural 1260 a nudnik photographer (DP)

A nudnik photographer

 

Note:

Sort the numbers from 1 to n. 1 must be at the leftmost. The difference between two adjacent numbers cannot exceed 2. How many sort methods are available.

 

Ideas:

DP for the seat, when the first is 1, the second is 2, the combination of DP [I-1]; when the first is 1, the second is 3, the third is also determined to be 2, combined as DP [I-3]; and the last case is 1357 ...... 8642.

So the DP equation is DP [I] = DP [I-1] + dp [I-3] + 1.

 

1 # include <stdio. h> 2 3 int N; 4 int DP [2, 100]; 5 6 int main () 7 {8 scanf ("% d", & N ); 9 DP [1] = 1; 10 DP [2] = 1; 11 DP [3] = 2; 12 DP [4] = 4; 13 for (INT I = 5; I <= 55; + I) {14 DP [I] = DP [I-1] + dp [I-3] + 1; 15} 16 printf ("% d ", DP [N]); 17 18 return 0; 19}

URL 1260