Package g1201_1300.s1269_number_of_ways_to_stay_in_the_same_place_after_some_steps

Class Solution

java.lang.Object
g1201_1300.s1269_number_of_ways_to_stay_in_the_same_place_after_some_steps.Solution
public class Solution extends java.lang.Object
1269 - Number of Ways to Stay in the Same Place After Some Steps.

Hard

You have a pointer at index 0 in an array of size arrLen. At each step, you can move 1 position to the left, 1 position to the right in the array, or stay in the same place (The pointer should not be placed outside the array at any time).

Given two integers steps and arrLen, return the number of ways such that your pointer still at index 0 after exactly steps steps. Since the answer may be too large, return it modulo 109 + 7.

Example 1:

Input: steps = 3, arrLen = 2

Output: 4

Explanation: There are 4 differents ways to stay at index 0 after 3 steps.

Right, Left, Stay

Stay, Right, Left

Right, Stay, Left

Stay, Stay, Stay

Example 2:

Input: steps = 2, arrLen = 4

Output: 2

Explanation: There are 2 differents ways to stay at index 0 after 2 steps

Right, Left

Stay, Stay

Example 3:

Input: steps = 4, arrLen = 2

Output: 8

Constraints:

  • 1 <= steps <= 500
  • 1 <= arrLen <= 106

  • Constructor Summary

    Constructors
    Constructor
    Description
    Solution()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    numWays(int steps, int arrLen)
     

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • numWays

      public int numWays(int steps, int arrLen)