Removing row or column wise duplicates from matrix of characters

Last Updated : 18 Nov, 2022

Given a matrix of characters containing only lowercase letters, form a new string from the matrix that remains after removing the duplicate characters from each row and column. The remaining characters are joined row-wise to form the string.

Examples:

Input : Matrix of characters (Or array
        of strings)
        aabcd
        effgh
        iijkk
        lmnoo
        pqqrs
        ttuvw
        xxyyz
Output : bcdeghjlmnprsuvwz
The characters that appear more than once
in their row or column are removed.

Input : zx
        xz
Output :zxxz

Approach: Traverse the entire matrix and for every element, check its corresponding row and column. If there are duplicates, then mark that particular cell in another matrix as true. Finally, all the characters for which there is a false value in another matrix are joined to form the string.

C++

// CPP code to form string after removing
// duplicates from rows and columns.
#include <bits/stdc++.h>
using namespace std;

// Function to check duplicates
// in row and column
void findDuplicates(string a[], int n, int m)
{
    // Create an array isPresent and initialize
    // all entries of it as false. The value of
    // isPresent[i][j] is going to be true if
    // s[i][j] is present in its row or column.
    bool isPresent[n][m];
    memset(isPresent, 0, sizeof(isPresent));

    for (int i = 0; i < n; i++) {
        for (int j = 0; j < m; j++) {

            // Checking every row for
            // duplicates of a[i][j]
            for (int k = 0; k < n; k++) {
                if (a[i][j] == a[k][j] && i != k) {
                    isPresent[i][j] = true;
                    isPresent[k][j] = true;
                }
            }

            // Checking every column for
            // duplicate characters
            for (int k = 0; k < m; k++) {
                if (a[i][j] == a[i][k] && j != k) {
                    isPresent[i][j] = true;
                    isPresent[i][k] = true;
                }
            }
        }
    }

    for (int i = 0; i < n; i++)
        for (int j = 0; j < m; j++)

            // If the character is unique
            // in its row and column
            if (!isPresent[i][j])
                printf("%c", a[i][j]);
}

// Driver code
int main()
{
    int n = 2, m = 5;

    // character array
    string a[] = { "zx", "xz" };

    // Calling function
    findDuplicates(a, n, m);
    return 0;
}

Java

// Java code to form string 
// after removing duplicates
// from rows and columns.

class GFG
{
    // Function to check 
    // duplicates in row 
    // and column
    static void findDuplicates(String []a, 
                            int n, int m)
    {
        // Create an array isPresent 
        // and initialize all entries 
        // of it as false. The value 
        // of isPresent[i,j] is going 
        // to be true if s[i,j] is 
        // present in its row or column.
        boolean [][]isPresent = new boolean[n] [m];
        
        for (int i = 0; i < n; i++)
        {
            for (int j = 0; j < m; j++) 
            {
    
                isPresent[i][j]=false;
            }
        }
    
        
        
        for (int i = 0; i < n; i++)
        {
            for (int j = 0; j < m; j++) 
            {
    
                // Checking every row for
                // duplicates of a[i,j]
                for (int k = 0; k < n; k++) 
                {
                    if (a[i].charAt(j)== a[k].charAt(j) && 
                                i != k) 
                    {
                        isPresent[i][j] = true;
                        isPresent[k][j] = true;
                    }
                }
    
                // Checking every column for
                // duplicate characters
                for (int k = 0; k < m; k++)
                {
                    if (a[i].charAt(j)== a[i].charAt(k) && 
                                j != k)
                    {
                        isPresent[i][j] = true;
                        isPresent[i][k] = true;
                    }
                }
            }
        }
        
        for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
    
                // If the character is 
                // unique in its row 
                // and column
                if (isPresent[i][j]==false)
                    System.out.print(a[i].charAt(j));
    }
    
    // Driver code
    public static void main(String []args)
    {
        int n = 2, m = 2;
    
        // character array
        String []a = new String[]{"zx", 
                                "xz"};

        // Calling function
        findDuplicates(a, n, m);
    }
}

// This code is contributed by 
// Hritik Raj( ihritik)

Python3

# Python3 code to form string after removing
# duplicates from rows and columns.

# Function to check duplicates
# in row and column
def findDuplicates(a, n, m):

    # Create an array isPresent and initialize
    # all entries of it as false. The value of
    # isPresent[i][j] is going to be true if
    # s[i][j] is present in its row or column.
    isPresent = [[False for i in range(n)] 
                        for j in range(m)]

    for i in range(n):
        for j in range(m):

            # Checking every row for
            # duplicates of a[i][j]
            for k in range(n):
                if i != k and a[i][j] == a[k][j]:
                    isPresent[i][j] = True
                    isPresent[k][j] = True

            # Checking every row for
            # duplicates of a[i][j]
            for k in range(m):
                if j != k and a[i][j] == a[i][k]:
                    isPresent[i][j] = True
                    isPresent[i][k] = True

    for i in range(n):
        for j in range(m):

            # If the character is unique
            # in its row and column
            if not isPresent[i][j]:
                print(a[i][j], end = "")

# Driver Code
if __name__ == "__main__":

    n = 2
    m = 2

    # character array
    a = ["zx", "xz"]

    # Calling function
    findDuplicates(a, n, m)

# This code is contributed by
# sanjeev2552

// C# code to form string 
// after removing duplicates
// from rows and columns.
using System;

class GFG
{
    // Function to check 
    // duplicates in row 
    // and column
    static void findDuplicates(string []a, 
                               int n, int m)
    {
        // Create an array isPresent 
        // and initialize all entries 
        // of it as false. The value 
        // of isPresent[i,j] is going 
        // to be true if s[i,j] is 
        // present in its row or column.
        bool [,]isPresent = new bool[n, m];
        
        for (int i = 0; i < n; i++)
        {
            for (int j = 0; j < m; j++) 
            {
    
                // Checking every row for
                // duplicates of a[i,j]
                for (int k = 0; k < n; k++) 
                {
                    if (a[i][j] == a[k][j] && 
                                   i != k) 
                    {
                        isPresent[i, j] = true;
                        isPresent[k, j] = true;
                    }
                }
    
                // Checking every column for
                // duplicate characters
                for (int k = 0; k < m; k++)
                {
                    if (a[i][j] == a[i][k] && 
                                   j != k)
                    {
                        isPresent[i, j] = true;
                        isPresent[i, k] = true;
                    }
                }
            }
        }
        
        for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
    
                // If the character is 
                // unique in its row 
                // and column
                if (!isPresent[i, j])
                    Console.Write(a[i][j]);
    }
    
    // Driver code
    static void Main()
    {
        int n = 2, m = 2;
    
        // character array
        string []a = new string[]{"zx", 
                                  "xz"};

        // Calling function
        findDuplicates(a, n, m);
    }
}

// This code is contributed by 
// Manish Shaw(manishshaw1)

JavaScript

<script>
// javascript code to form string 
// after removing duplicates
// from rows and columns.    // Function to check
    // duplicates in row
    // and column
    function findDuplicates( a , n , m) {
        // Create an array isPresent
        // and initialize all entries
        // of it as false. The value
        // of isPresent[i,j] is going
        // to be true if s[i,j] is
        // present in its row or column.
        var isPresent = Array(n).fill().map(() => Array(m).fill(0));

        for (var i = 0; i < n; i++) {
            for (var j = 0; j < m; j++) {

                isPresent[i][j] = false;
            }
        }

        for (var i = 0; i < n; i++) {
            for (var j = 0; j < m; j++) {

                // Checking every row for
                // duplicates of a[i,j]
                for (var k = 0; k < n; k++) {
                    if (a[i].charAt(j) == a[k].charAt(j) && i != k) {
                        isPresent[i][j] = true;
                        isPresent[k][j] = true;
                    }
                }

                // Checking every column for
                // duplicate characters
                for (k = 0; k < m; k++) {
                    if (a[i].charAt(j) == a[i].charAt(k) && j != k) {
                        isPresent[i][j] = true;
                        isPresent[i][k] = true;
                    }
                }
            }
        }

        for (var i = 0; i < n; i++)
            for (var j = 0; j < m; j++)

                // If the character is
                // unique in its row
                // and column
                if (isPresent[i][j] == false)
                    document.write(a[i].charAt(j));
    }

    // Driver code
    
        var n = 2, m = 2;

        // character array
        var a = [ "zx", "xz" ];

        // Calling function
        findDuplicates(a, n, m);

// This code contributed by umadevi9616 
</script>

Output

zxxz

Time Complexity: O(n * m * (n + m)), where n and m are the numbers of rows and columns.
Auxiliary Space: O(n * m), where n and m are the numbers of rows and columns.

Removing row or column wise duplicates from matrix of characters

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Removing row or column wise duplicates from matrix of characters

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