Method push

155. Min Stack/src/main.rs:24–29

(&mut self, x: i32)

    }
    
    fn push(&mut self, x: i32) {
        self.s.push(x);
        if self.ms.is_empty() || self.ms.last().unwrap() >= &x {
            self.ms.push(x);
        }
    }
    
    fn pop(&mut self) {
        if let Some(x) = self.s.pop() {