3179. Find the N-th Value After K Seconds
You are given two integers
nandk.Initially, you start with an array
aofnintegers wherea[i] = 1for all0 <= 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]becomesa[0] + a[1],a[2]becomesa[0] + a[1] + a[2], and so on.Return the value of
a[n - 1]afterkseconds.Since the answer may be very large, return it modulo
109 + 7.