Package g3101_3200.s3179_find_the_n_th_value_after_k_seconds

Class Solution

java.lang.Object
g3101_3200.s3179_find_the_n_th_value_after_k_seconds.Solution
public class Solution extends Object
3179 - Find the N-th Value After K Seconds.

Medium

You are given two integers n and k.

Initially, you start with an array a of n integers where a[i] = 1 for all 0 <= i <= n - 1. After each second, you simultaneously update each element to be the sum of all its preceding elements plus the element itself. For example, after one second, a[0] remains the same, a[1] becomes a[0] + a[1], a[2] becomes a[0] + a[1] + a[2], and so on.

Return the value of a[n - 1] after k seconds.

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

Example 1:

Input: n = 4, k = 5

Output: 56

Explanation:

SecondState After
0[1, 1, 1, 1]
1[1, 2, 3, 4]
2[1, 3, 6, 10]
3[1, 4, 10, 20]
4[1, 5, 15, 35]
5[1, 6, 21, 56]

Example 2:

Input: n = 5, k = 3

Output: 35

Explanation:

SecondState After
0[1, 1, 1, 1, 1]
1[1, 2, 3, 4, 5]
2[1, 3, 6, 10, 15]
3[1, 4, 10, 20, 35]

Constraints:

  • 1 <= n, k <= 1000

  • Constructor Details

    • Solution

      public Solution()

  • Method Details

    • valueAfterKSeconds

      public int valueAfterKSeconds(int n, int k)