/*
 * @lc app=leetcode id=1299 lang=rust
 *
 * [1299] Replace Elements with Greatest Element on Right Side
 *
 * https://leetcode.com/problems/replace-elements-with-greatest-element-on-right-side/description/
 *
 * algorithms
 * Easy (77.50%)
 * Total Accepted:    17.6K
 * Total Submissions: 22.7K
 * Testcase Example:  '[17,18,5,4,6,1]'
 *
 * Given an array arr, replace every element in that array with the greatest
 * element among the elements to its right, and replace the last element with
 * -1.
 * 
 * After doing so, return the array.
 * 
 * 
 * Example 1:
 * Input: arr = [17,18,5,4,6,1]
 * Output: [18,6,6,6,1,-1]
 * 
 * 
 * Constraints:
 * 
 * 
 * 1 <= arr.length <= 10^4
 * 1 <= arr[i] <= 10^5
 * 
 */
impl Solution {
    pub fn replace_elements(mut arr: Vec<i32>) -> Vec<i32> {
        let mut premax = -1; 
        for i in arr.iter_mut().rev(){
            let t = *i; 
            *i = premax; 
            premax = max(premax, t);
        }
        arr
    }
}
// pub structSolution; 
use std::collections::HashMap;
use std::fmt::Debug;
use std::hash::Hash;
use std::cmp::max; 
use std::cmp::min; 

#[allow(dead_code)]
pub fn print_map<K: Debug + Eq + Hash, V: Debug>(map: &HashMap<K, V>) {
    for (k, v) in map.iter() {
        println!("{:?}: {:?}", k, v);
    }
}

#[allow(dead_code)]
pub fn say_vec(nums: Vec<i32>){
	println!("{:?}", nums);
}

#[allow(dead_code)]
pub fn char_frequency(s: String) -> HashMap<char, i32> {
    let mut res:HashMap<char, i32> = HashMap::new(); 
    for c in s.chars(){
        *res.entry(c).or_insert(0) += 1;
    }
    res 
}