LeetCode 673 Number of Longest Increasing Subsequences - Walkthrough

Count LIS in $[1, 3, 5, 4, 7]$. Track $dp[i]$ = length, $count[i]$ = number of LIS ending at $i$. $dp = [1, 2, 3, 3, 4]$. For $count$: position $0$ has $1$. Position $1$: extends from $0$, so $count[1] = 1$.

Position $2$: extends from $1$, $count[2] = 1$. Position $3$: extends from $1$, $count[3] = 1$. Position $4$: extends from $2$ or $3$ (both length $3$), so $count[4] = count[2] + count[3] = 2$. Max length is $4$ (only at position $4$). Total LIS count: $count[4] = 2$. They are $[1, 3, 5, 7]$ and $[1, 3, 4, 7]$.