LeetCode 496. Next Greater Element I

Problem Statement

use std::collections::{HashMap, VecDeque};
impl Solution {
    pub fn next_greater_element(nums1: Vec<i32>, nums2: Vec<i32>) -> Vec<i32> {
        let mut ans = vec![];
        let mut stack: Vec<i32> = vec![];
        let mut m = HashMap::new();

        for num in nums2 {
            while !stack.is_empty() {
                let cur = stack.last().unwrap().clone();
                if cur >= num {
                    break;
                }

                m.entry(cur).or_insert(0);
                *m.get_mut(&cur).unwrap() = num;
                stack.pop();
            }
            stack.push(num);
        }

        for num in nums1 {
            if m.contains_key(&num) {
                ans.push(*m.get(&num).unwrap());
            } else {
                ans.push(-1);
            }
        }
        return ans;
    }
}