Package g1201_1300.s1269_number_of_ways_to_stay_in_the_same_place_after_some_steps

Class Solution

  • All Implemented Interfaces:
    
public final class Solution

    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 <code>10<sup>9</sup> + 7</code>.

    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 &lt;= steps &lt;= 500

    • <code>1 <= arrLen <= 10<sup>6</sup></code>

    • Nested Class Summary

      Nested Classes 
      Modifier and Type Class Description

    • Field Summary

      Fields 
      Modifier and Type Field Description

    • Constructor Summary

      Constructors 
      Constructor Description
      Solution()

    • Enum Constant Summary

      Enum Constants 
      Enum Constant Description

    • Method Summary

      Modifier and Type Method Description
      final Integer numWays(Integer steps, Integer arrLen)

      • Methods inherited from class java.lang.Object

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