Question 1: User ID Generation

Problem 1 User Id Generation

Topics Involved / Prerequisites

• String Manipulation

• ASCII / Case Toggling

Overview

1. We first determine the shorter and longer names by comparing their lengths, using alphabetical order as a strict tie-breaker.
2. Next, we extract the required characters and PIN digits using simple 0-based index mathematics to build our raw user ID string.
3. Finally, we loop through this newly constructed string and swap the uppercase and lowercase letters using standard character functions.

Approach

1. Sorting the Names

This is a fantastic string manipulation challenge that tests your attention to detail! Picture a scenario where you are building a secure registration system; the rules might seem arbitrary, but breaking them down step-by-step makes the code write itself. We first check the lengths of the first and last names. If they are exactly the same length, we can just use the standard < operator in C++, which automatically compares strings in alphabetical (lexicographical) order for us!

2. Building and Toggling

When extracting the Nth digit from the PIN, remember that strings in C++ are 0-indexed, but the problem gives N as a 1-based position. So, the N-th digit from the left is at index N - 1, and the Nth digit from the right is at length - N. Once we glue the pieces together, we just loop through the final string and use the built-in islower(), toupper(), isupper(), and tolower() functions to flip the capitalization.

C++ Code-:

#include <iostream>
#include <string>
#include <cctype>

using namespace std;

string generateUserId(string first, string last, string pin, int n) {
    string smaller, longer;
    
    // Step 1: Find smaller and longer names
    if (first.length() < last.length()) {
        smaller = first;
        longer = last;
    } else if (first.length() > last.length()) {
        smaller = last;
        longer = first;
    } else {
        // Tie-breaker: alphabetical order
        if (first < last) {
            smaller = first;
            longer = last;
        } else {
            smaller = last;
            longer = first;
        }
    }
    
    // Step 2: Build the raw user-id
    char lastChar = longer[longer.length() - 1];
    char leftDigit = pin[n - 1];
    char rightDigit = pin[pin.length() - n];
    
    string rawId = "";
    rawId += lastChar;
    rawId += smaller;
    rawId += leftDigit;
    rawId += rightDigit;
    
    // Step 3: Toggle the cases
    for (int i = 0; i < rawId.length(); i++) {
        if (islower(rawId[i])) {
            rawId[i] = toupper(rawId[i]);
        } else if (isupper(rawId[i])) {
            rawId[i] = tolower(rawId[i]);
        }
    }
    
    return rawId;
}

Time Complexity

• Time: O(L) - Where L is the combined length of the names, as string comparison and case toggling scale linearly with the length of the words.

• Space: O(L) - To store and build the newly generated user ID string.