Leetcode 496. Next Greater Element I

gistfile1.txt

class Solution {
    public int[] nextGreaterElement(int[] nums1, int[] nums2) {
        Map<Integer, Integer> map = new HashMap<>();
        
        for(int i = 0; i < nums2.length; i++) {
            map.put(nums2[i], i);
        }
        
        Stack<Integer> stack = new Stack<>();
        for(int i = 0; i < nums2.length; i++) {
            while(!stack.isEmpty() && nums2[stack.peek()] < nums2[i]) {
                nums2[stack.pop()] = nums2[i];
            }
            stack.push(i);
        }
        
        //we cannot find next greater so set it to -1
        while(!stack.isEmpty()) {
            nums2[stack.pop()] = -1;
        }
        
        for(int i = 0; i < nums1.length; i++) {
            nums1[i] = nums2[map.get(nums1[i])];
        }
        
        return nums1;
    }
}