Module 4Stack, Queue & DequeLesson 15 of 2318 min

Stack with Vec

push/pop back; valid parentheses; monotonic stack intro.

Stack = Vec

rust

fn main() {
    let mut st = Vec::new();
    st.push(1);
    st.push(2);
    st.push(3);
    println!("peek={:?}", st.last());
    println!("pop={:?}", st.pop());
    println!("stack={st:?}");
}

Output

peek=Some(3)
pop=Some(3)
stack=[1, 2]

Valid parentheses

Push openers; on closer, pop and match.

Monotonic stack (preview)

Keep increasing/decreasing stack of indices for next greater element — O(n).

Challenge

Next greater element: for each nums[i], find first greater to the right (-1 if none).

Tips

last() peeks
pop returns Option
Empty stack edge cases

Try it live

Stack with VecRust 2021

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Output

Press Run to compile and execute.