Minimum moves to make count of lowercase and uppercase letters equal

Given a string, S of even length N, the task is to find the minimum number of moves needed to convert the string to a string consisting of half upper case and half lower case characters.

Examples: 

Input: S = “AbcdEf”
Output:  1 
               ABcdEf
Explanation: 
One possible way to modify the string is by converting the second character to S[1]( =’b’) to an uppercase character. Thereafter, the string modifies to “ABcdEf” which consists of 3 lower case and upper case characters.

Input: S = “ABCdef”
Output:  0
               ABCdef

Approach: The idea is to convert only those characters that are extra in any of the cases. Follow the steps below to solve the problem:

• Find the count of the upper case English alphabet and lower case English alphabet and store them in variables, say upper and lower respectively.
• Initialize a variable, say moves as 0, to store the minimum number of moves to modify the string.
• If upper case characters are more, then traverse the string and convert upper case characters into the lower case until both cases characters are equal in number.
• Otherwise, if the lower case characters are more, traverse the string S and convert the lower case characters into the upper case until both cases characters are equal in number.
• Finally, after completing the above steps, print the value of moves as the answer and string S as the modified string.

Below is the implementation of the above approach:

C++

// C++ program for the above approach
#include <bits/stdc++.h>
using namespace std;

// Function to calculate minimum
// number of moves required to
// convert the string
void minimumTimeToConvertString(string S, int N)
{
    // Stores Count of upper and
    // lower case characters
    int upper = 0, lower = 0;

    // Traverse the string S
    for (int i = 0; i < N; i++) {

        char c = S[i];

        // If current character is
        // uppercase
        if (isupper(c)) {

            // Increment count
            // of Uppercase characters
            upper++;
        }
        // Otherwise,
        else {

            // Increment count
            // of Lowercase characters
            lower++;
        }
    }

    // Stores minimum number of moves needed
    int moves = 0;

    // If there are more upper
    // case characters
    if (upper > N / 2) {

        int i = 0;
        // Iterate until upper is greater
        // than N/2
        while (upper > N / 2 && i < N) {

            // Convert uppercase into
            // lowercase until upper=N/2
            if (isupper(S[i])) {

                S[i] += 32;
                moves++;
                upper--;
                lower++;
            }

            // Increment the pointer
            i++;
        }
    }
    // If there are more lower
    // case characters
    else if (lower > N / 2) {

        int i = 0;
        // Iterate until lower is greater
        // than N/2
        while (lower > N / 2 && i < N) {

            // Convert lowercase into
            // uppercase until lower=N/2
            if (islower(S[i])) {

                S[i] -= 32;
                moves++;
                upper++;
                lower--;
            }

            // Increment the pointer
            i++;
        }
    }

    // Print moves required
    cout << moves << endl;

    // Print resultant string
    cout << S << endl;
}

// Driver Code
int main()
{
    // Given string
    string S = "AbcdEf";
    int N = S.length();

    // Function call
    minimumTimeToConvertString(S, N);

    return 0;
}

Java

// Java program for the above approach
class GFG{

// Function to calculate minimum
// number of moves required to
// convert the string
static void minimumTimeToConvertString(String S, int N)
{

    // Stores Count of upper and
    // lower case characters
    int upper = 0, lower = 0;

    // Traverse the string S
    for(int i = 0; i < N; i++)
    {
        char c = S.charAt(i);

        // If current character is
        // uppercase
        if (Character.isUpperCase(c))
        {

            // Increment count
            // of Uppercase characters
            upper++;
        }

        // Otherwise,
        else
        {

            // Increment count
            // of Lowercase characters
            lower++;
        }
    }

    // Stores minimum number of moves needed
    int moves = 0;

    // If there are more upper
    // case characters
    if (upper > N / 2)
    {
        int i = 0;

        // Iterate until upper is greater
        // than N/2
        while (upper > N / 2 && i < N)
        {

            // Convert uppercase into
            // lowercase until upper=N/2
            if (Character.isUpperCase(S.charAt(i)))
            {
                S = S.substring(0, i) +
                   (char)(S.charAt(i) + 32) +
                        S.substring(i + 1);
                moves++;
                upper--;
                lower++;
            }

            // Increment the pointer
            i++;
        }
    }

    // If there are more lower
    // case characters
    else if (lower > N / 2)
    {
        int i = 0;

        // Iterate until lower is greater
        // than N/2
        while (lower > N / 2 && i < N)
        {

            // Convert lowercase into
            // uppercase until lower=N/2
            if (Character.isLowerCase(S.charAt(i)))
            {
                S = S.substring(0, i) +
                   (char)(S.charAt(i) - 32) +
                        S.substring(i + 1);

                moves++;
                upper++;
                lower--;
            }

            // Increment the pointer
            i++;
        }
    }

    // Print moves required
    System.out.println(moves);

    // Print resultant string
    System.out.println(S);
}

// Driver code
public static void main(String[] args)
{

    // Given string
    String S = "AbcdEf";
    int N = S.length();

    // Function call
    minimumTimeToConvertString(S, N);
}
}

// This code is contributed by abhinavjain194

Python3

# Python3 program for the above approach

# Function to calculate minimum
# number of moves required to
# convert the string
def minimumTimeToConvertString(S, N):

    S = [i for i in S]

    # Stores Count of upper and
    # lower case characters
    upper = 0
    lower = 0

    # Traverse the S
    for i in range(N):
        c = S[i]

        # If current character is
        # uppercase
        if (c.isupper()):

            # Increment count
            # of Uppercase characters
            upper += 1

        # Otherwise,
        else:

            # Increment count
            # of Lowercase characters
            lower += 1

    # Stores minimum number of moves needed
    moves = 0

    # If there are more upper
    # case characters
    if (upper > N // 2):
        i = 0

        # Iterate until upper is greater
        # than N/2
        while (upper > N // 2 and i < N):

            # Convert uppercase into
            # lowercase until upper=N/2
            if (S[i].isupper()):
                S[i] += 32
                moves += 1
                upper -= 1
                lower += 1

            # Increment the pointer
            i += 1

    # If there are more lower
    # case characters
    elif (lower > N // 2):
        i = 0

        # Iterate until lower is greater
        # than N/2
        while (lower > N // 2 and i < N):

            # Convert lowercase into
            # uppercase until lower=N/2
            if (S[i].islower()):
                S[i] = chr(ord(S[i]) - 32)
                moves += 1
                upper += 1
                lower -= 1

            # Increment the pointer
            i += 1

    # Print moves required
    print(moves)

    # Print resultant string
    print("".join(S))

# Driver Code
if __name__ == '__main__':

    # Given string
    S = "AbcdEf"
    N = len(S)

    # Function call
    minimumTimeToConvertString(S, N)

# This code is contributed by mohit kumar 29

C#

// C# program for the above approach
using System;
class GFG {

    // Function to calculate minimum
    // number of moves required to
    // convert the string
    static void minimumTimeToConvertString(char[] S, int N)
    {
        // Stores Count of upper and
        // lower case characters
        int upper = 0, lower = 0;

        // Traverse the string S
        for (int i = 0; i < N; i++) {

            char c = S[i];

            // If current character is
            // uppercase
            if (Char.IsUpper(c)) {

                // Increment count
                // of Uppercase characters
                upper++;
            }
            // Otherwise,
            else {

                // Increment count
                // of Lowercase characters
                lower++;
            }
        }

        // Stores minimum number of moves needed
        int moves = 0;

        // If there are more upper
        // case characters
        if (upper > N / 2) {

            int i = 0;
            // Iterate until upper is greater
            // than N/2
            while (upper > N / 2 && i < N) {

                // Convert uppercase into
                // lowercase until upper=N/2
                if (Char.IsUpper(S[i])) {

                    S[i] += (char)32;
                    moves++;
                    upper--;
                    lower++;
                }

                // Increment the pointer
                i++;
            }
        }
        // If there are more lower
        // case characters
        else if (lower > N / 2) {

            int i = 0;
            // Iterate until lower is greater
            // than N/2
            while (lower > N / 2 && i < N) {

                // Convert lowercase into
                // uppercase until lower=N/2
                if (Char.IsLower(S[i])) {

                    S[i] = (char)((int)S[i] - 32);
                    moves++;
                    upper++;
                    lower--;
                }

                // Increment the pointer
                i++;
            }
        }

        // Print moves required
        Console.WriteLine(moves);

        // Print resultant string
        Console.WriteLine(new string(S));
    }

  static void Main() {
    // Given string
    string S = "AbcdEf";
    int N = S.Length;

    // Function call
    minimumTimeToConvertString(S.ToCharArray(), N);
  }
}

// This code is contributed by mukesh07.

Javascript

<script>
    // Javascript program for the above approach

    // Function to calculate minimum
    // number of moves required to
    // convert the string
    function minimumTimeToConvertString(S, N)
    {

        // Stores Count of upper and
        // lower case characters
        let upper = 0, lower = 0;

        // Traverse the string S
        for (let i = 0; i < N; i++) {

            let c = S[i];

            // If current character is
            // uppercase
            if (c == c.toUpperCase()) {

                // Increment count
                // of Uppercase characters
                upper++;
            }
            // Otherwise,
            else {

                // Increment count
                // of Lowercase characters
                lower++;
            }
        }

        // Stores minimum number of moves needed
        let moves = 0;

        // If there are more upper
        // case characters
        if (upper > parseInt(N / 2, 10)) {

            let i = 0;
            // Iterate until upper is greater
            // than N/2
            while (upper > parseInt(N / 2, 10) && i < N) {

                // Convert uppercase into
                // lowercase until upper=N/2
                if (S[i] == S[i].toUpperCase()) {

                    S[i] += String.fromCharCode(32);
                    moves++;
                    upper--;
                    lower++;
                }

                // Increment the pointer
                i++;
            }
        }
        // If there are more lower
        // case characters
        else if (lower > parseInt(N / 2, 10)) {

            let i = 0;
            // Iterate until lower is greater
            // than N/2
            while (lower > parseInt(N / 2, 10) && i < N) {

                // Convert lowercase into
                // uppercase until lower=N/2
                if (S[i] == S[i].toLowerCase()) {

                    S[i] = String.fromCharCode(S[i].charCodeAt() - 32);
                    moves++;
                    upper++;
                    lower--;
                }

                // Increment the pointer
                i++;
            }
        }

        // Print moves required
        document.write(moves + "</br>");

        // Print resultant string
        document.write(S.join(""));
    }

    // Given string
    let S = "AbcdEf";
    let N = S.length;

    // Function call
    minimumTimeToConvertString(S.split(''), N);

   // This code is contributed by decode2207.
</script>

Output

1
ABcdEf

Time Complexity: O(N)
Auxiliary Space: O(1)