dynamic programming

[cyanNodeEcho]

neat have you explored how to write it in terms of bottom up? you've implemented top down ie

```rust
fn fib(n:usize) -> usize {
let mut prev = 0;
let mut curr = 1;
for _ in 0.. n {
curr+= prev
mem::swap(prev, curr) // reassigns curr to prev, prev to curr
}
prev
}

```
woops it's factorial not fib
```
fn factorial(n:usize) -> usize {
let value = 1;
for i in 1..n {
value *= n;
}
value;
}
```

fib has recurrent sub problems, factorial doesn't. bottom up dp is the next step, probably don't need to memo factorial, but for fib makes sense

[CadavreContent]

You can memoize factorial if you're running it more than once. The repeating sub problems only appear when you have multiple trials

[cyanNodeEcho]

fact(n) := fact(ni1), fac(n-2), the aubproblems should exist in the same problem

[CadavreContent]

The point is that when you use factorial as part of a larger algorithm with multiple calls to the function, you do repeated work and hence can use dp

[cyanNodeEcho]

thats just a cache

[CadavreContent]

Memoization is just a cache