HashMap.rs

use std::collections::HashMap;

structFreqStack{
num_freq:HashMap<i32,i32>,
freq_stack:HashMap<i32,Vec<i32>>,
max_freq:i32,
}


/** 
 * `&self` means the method takes an immutable reference.
 * If you need a mutable reference, change it to `&mut self` instead.
 */
implFreqStack{

fnnew() -> Self{
Self{
num_freq:HashMap::new(),
freq_stack:HashMap::new(),
max_freq:0,
}
}

fnpush(&mutself,x:i32){
let freq = self.num_freq.entry(x).or_default();
*freq += 1;
self.freq_stack.entry(*freq).or_default().push(x);
self.max_freq = self.max_freq.max(*freq);
}

fnpop(&mutself) -> i32{
let stack = self.freq_stack.get_mut(&self.max_freq).unwrap();
let x = stack.pop().unwrap();
*self.num_freq.get_mut(&x).unwrap() -= 1;
if stack.is_empty(){
self.max_freq -= 1;
}
 x
}
}

/**
 * Your FreqStack object will be instantiated and called as such:
 * let obj = FreqStack::new();
 * obj.push(x);
 * let ret_2: i32 = obj.pop();
 */