484.Find Permutation

1- Greedy Using Stack

Can also use reverse array

Two pointer

https://leetcode.com/problems/find-permutation/solution/

class Solution {
    public int[] findPermutation(String s) {
        int[] ans = new int[s.length() + 1];
        Deque<Integer> stack = new ArrayDeque<>();
        int ansIndex = 0;
        for(int i = 1; i <= s.length(); i++){
            if(s.charAt(i - 1) == 'I'){
                stack.push(i);
                while(!stack.isEmpty()){
                    ans[ansIndex] = stack.pop();
                    ansIndex++;
                }
            }
            else{
                stack.push(i);
            }
        }
        stack.push(s.length() + 1);
        while(!stack.isEmpty()){
            ans[ansIndex++] = stack.pop();
        }
        return ans;
    }
}