You are given a 0-indexed string pattern of length n consisting of the characters 'I' meaning increasing and 'D' meaning decreasing. A 0-indexed string num of length n + 1 is created using the following conditions: num consists of the digits '1' to

smallestNumber.js

/**
 * @param {string} pattern
 * @return {string}
 */
var smallestNumber = function(pattern) {
    const n = pattern.length;
    const result = [];
    const stack = [];

    for (let i = 0; i <= n; i++) {
        // Push the current number onto the stack
        stack.push(i + 1);

        // If we reach the end or find an 'I', process the stack
        if (i === n || pattern[i] === 'I') {
            // Pop elements from the stack and add to result
            while (stack.length) {
                result.push(stack.pop());
            }
        }
    }

    // Convert the result array to a string and return
    return result.join('');
};