g0901_1000.s0935_knight_dialer

Class Solution

java.lang.Object

g0901_1000.s0935_knight_dialer.Solution

public class Solution
extends Object

935 - Knight Dialer.

Medium

The chess knight has a unique movement , it may move two squares vertically and one square horizontally, or two squares horizontally and one square vertically (with both forming the shape of an L ). The possible movements of chess knight are shown in this diagaram:

A chess knight can move as indicated in the chess diagram below:

We have a chess knight and a phone pad as shown below, the knight can only stand on a numeric cell (i.e. blue cell).

Given an integer n, return how many distinct phone numbers of length n we can dial.

You are allowed to place the knight on any numeric cell initially and then you should perform n - 1 jumps to dial a number of length n. All jumps should be valid knight jumps.

As the answer may be very large, return the answer modulo 109 + 7.

Example 1:

Input: n = 1

Output: 10

Explanation: We need to dial a number of length 1, so placing the knight over any numeric cell of the 10 cells is sufficient.

Example 2:

Input: n = 2

Output: 20

Explanation: All the valid number we can dial are [04, 06, 16, 18, 27, 29, 34, 38, 40, 43, 49, 60, 61, 67, 72, 76, 81, 83, 92, 94]

Example 3:

Input: n = 3131

Output: 136006598

Explanation: Please take care of the mod.

Constraints:

• 1 <= n <= 5000

Constructor Summary

Constructors

Constructor and Description
Solution()

Method Summary

Modifier and Type	Method and Description
int	knightDialer(int n)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Solution

public Solution()

Method Detail

knightDialer

public int knightDialer(int n)