Construct Smallest Number From DI String | Leetcode 2375

class Solution {
public:
    string smallestNumber(string pattern) {
        int n=pattern.size();
        stack<int> st;
        string res="";

        for(int i=1;i<=n+1;++i){
            st.push(i);
            char c = pattern[i-1];

            //If increasing then reverse and save
            if(i==n+1 or c=='I'){
                while(!st.empty()){
                    res.push_back(char('0'+st.top()));
                    st.pop();
                }
            }
        }
        return res;
    }
};
/*
//JAVA
import java.util.Stack;

class Solution {
    public String smallestNumber(String pattern) {
        int n = pattern.length();
        Stack<Integer> st = new Stack<>();
        StringBuilder res = new StringBuilder();

        for (int i = 1; i <= n + 1; ++i) {
            st.push(i);
            if (i == n + 1 || pattern.charAt(i - 1) == 'I') {
                while (!st.isEmpty()) {
                    res.append(st.pop());
                }
            }
        }

        return res.toString();
    }
}

#Python
class Solution:
    def smallestNumber(self, pattern: str) -> str:
        n = len(pattern)
        st = []
        res = []

        for i in range(1, n + 2):
            st.append(i)
            if i == n + 1 or pattern[i - 1] == 'I':
                while st:
                    res.append(str(st.pop()))

        return ''.join(res)

*/

What is the complexity.?

What is the complexity.?

O(N) for both TC and SC