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Calculate sum of the main diagonal and the number of rows and columns containing repeated values in a square matrix
  • Last Updated : 08 Apr, 2021

Given a matrix M[][] of dimensions N * N, consisting only of integers from the range 1 to N, the task is to compute the sum of the matrix elements present in the main diagonal, the number of rows and columns containing repeated values.

Examples:

Input: N = 4, M[][] = {{1, 2, 3, 4}, {2, 1, 4, 3}, {3, 4, 1, 2}, {4, 3, 2, 1}}
Output: 4 0 0
Explanation:
Sum of diagonal = M[0][0] + M[1][1] + M[2][2] + M[3][3] = 4.
No row or column consists of repeated elements.
Therefore, the required sum is 4

Input: N = 3, M[][] = {{2, 1, 3}, {1, 3, 2}, {1, 2, 3}}
Output: 8 0 2
Explanation:
Sum of diagonal = M[0][0]+M[1][1]+M[2][2] = 8.
No row consists of repeated elements.
1st and 3rd columns consists of repeated elements.

Approach: The approach is to simply traverse all elements of the matrix and find the sum of diagonals and the number of rows and columns having repeated values. Follow the steps below to solve the given problem:



  • Initialize variables trace, rowRepeat, and columnRepeat to store the sum of the main diagonal, the number of rows, and columns containing repeated matrix elements respectively.
  • Traverse through each element present in the matrix M[i][j] and increment the sum trace if i is equal to j.
  • To find rows containing repeated values, iterate over one row at a time, compare values, and check if there exists a repeated value or not. On getting the first pair of repeat element, increment rowRepeat by 1 and break out of the loop.
  • Repeat the above steps for every row of the matrix.
  • The same procedure is repeated for all columns, where columnRepeat is incremented by 1 if the values match.
  • After completing all the iterations, print the value of trace, rowRepeat, and columnRepeat as the result.

Below is the implementation of the above approach:

C++14




// C++14 program for the above approach
#include <bits/stdc++.h>
using namespace std;
 
// Function to calculate trace of
// a matrix and number of rows and
// columns with repeated elements
void vestigium(int N, int M[4][4])
{
     
    // Stores the trace, number of
    // rows and columns consisting
    // of repeated matrix elements
    int trace = 0, row_repeat = 0;
    int column_repeat = 0;
 
    // Iterate over the matrix
    for(int i = 0; i < N; i++)
    {
        for(int j = 0; j < N; j++)
        {
             
            // If current element is
            // present in the main diagonal
            if (i == j)
            {
                 
                // Update trace
                trace += M[i][j];
            }
        }
 
        int flag1 = 0;
 
        // Iterate over each row
        // and increment row_repeat
        // if repeated values exists
        for(int j = 0; j < N; j++)
        {
            for(int k = 0; k < N; k++)
            {
                 
                // For each valid range
                if (j != k && M[i][j] == M[i][k])
                {
                    row_repeat++;
                    flag1 = 1;
                    break;
                }
            }
 
            if (flag1 == 1)
            {
                break;
            }
        }
 
        int flag2 = 0;
 
        // Iterate over each column and
        // increment column_repeat if
        // repeated values are encountered
        for(int j = 0; j < N; j++)
        {
            for(int k = 0; k < N; k++)
            {
                 
                // For each valid range
                if (j != k && M[j][i] == M[k][i])
                {
                    column_repeat++;
                    flag2 = 1;
                    break;
                }
            }
 
            if (flag2 == 1)
            {
                break;
            }
        }
    }
 
    // Answer
    cout << trace << " "
         << row_repeat << " "
         << column_repeat ;
}
 
// Driver Code
int main()
{
    int M[4][4] = { { 1, 2, 3, 4 },
                    { 2, 1, 4, 3 },
                    { 3, 4, 1, 2 },
                    { 4, 3, 2, 1 } };
                       
    int N = sizeof(M) / sizeof(M[0]);
 
    vestigium(N, M);
}
 
// This code is contributed by sanjoy_62

Java




// Java program for the above approach
public class GFG {
 
    // Function to calculate trace of
    // a matrix and number of rows and
    // columns with repeated elements
    public static String vestigium(
        int N, int M[][])
    {
        // Stores the trace, number of
        // rows and columns consisting
        // of repeated matrix elements
        int trace = 0, row_repeat = 0;
        int column_repeat = 0;
 
        // Iterate over the matrix
        for (int i = 0; i < N; i++) {
 
            for (int j = 0; j < N; j++) {
 
                // If current element is
                // present in the main diagonal
                if (i == j) {
 
                    // Update trace
                    trace += M[i][j];
                }
            }
 
            int flag1 = 0;
 
            // Iterate over each row
            // and increment row_repeat
            // if repeated values exists
            for (int j = 0; j < N; j++) {
                for (int k = 0; k < N; k++) {
 
                    // For each valid range
                    if (j != k
                        && M[i][j] == M[i][k]) {
                        row_repeat++;
                        flag1 = 1;
                        break;
                    }
                }
 
                if (flag1 == 1) {
 
                    break;
                }
            }
 
            int flag2 = 0;
 
            // Iterate over each column and
            // increment column_repeat if
            // repeated values are encountered
            for (int j = 0; j < N; j++) {
                for (int k = 0; k < N; k++) {
 
                    // For each valid range
                    if (j != k
                        && M[j][i] == M[k][i]) {
 
                        column_repeat++;
                        flag2 = 1;
                        break;
                    }
                }
 
                if (flag2 == 1) {
 
                    break;
                }
            }
        }
 
        // Answer
        String output = trace + " "
                        + row_repeat + " "
                        + column_repeat + "\n";
 
        // Return answer
        return output;
    }
 
    // Driver Code
    public static void main(String[] args)
    {
        int M[][] = { { 1, 2, 3, 4 },
                      { 2, 1, 4, 3 },
                      { 3, 4, 1, 2 },
                      { 4, 3, 2, 1 } };
        int N = M.length;
 
        String output = vestigium(N, M);
 
        // Print the output
        System.out.print(output);
    }
}

Python3




# Python3 program for the above approach
 
# Function to calculate trace of
# a matrix and number of rows and
# columns with repeated elements
def vestigium(N, M) :
     
    # Stores the trace, number of
    # rows and columns consisting
    # of repeated matrix elements
    trace = 0
    row_repeat = 0
    column_repeat = 0
 
    # Iterate over the matrix
    for i in range(N) :
        for j in range(N) :
             
            # If current element is
            # present in the main diagonal
            if (i == j):
                 
                # Update trace
                trace += M[i][j]
        flag1 = 0
 
        # Iterate over each row
        # and increment row_repeat
        # if repeated values exists
        for j in range(N) :
            for k in range(N) :
                 
                # For each valid range
                if (j != k and M[i][j] == M[i][k]) :
                    row_repeat += 1
                    flag1 = 1
                    break
            if (flag1 == 1) :
                break
        flag2 = 0
 
        # Iterate over each column and
        # increment column_repeat if
        # repeated values are encountered
        for j in range(N) :
            for k in range(N) :
                 
                # For each valid range
                if (j != k and M[j][i] == M[k][i]) :
                    column_repeat += 1
                    flag2 = 1
                    break
                 
            if (flag2 == 1) :
                break
 
    # Answer
    print(trace, row_repeat, column_repeat)
 
# Driver Code
M = [[ 1, 2, 3, 4 ],
    [ 2, 1, 4, 3 ],
    [ 3, 4, 1, 2 ],
    [ 4, 3, 2, 1 ]]           
N = len(M)
vestigium(N, M)
 
# This code is contributed by avijitmonald1998.

C#




// C# program for the above approach
using System;
 
class GFG{
 
// Function to calculate trace of
// a matrix and number of rows and
// columns with repeated elements
public static String vestigium(int N, int[,] M)
{
     
    // Stores the trace, number of
    // rows and columns consisting
    // of repeated matrix elements
    int trace = 0, row_repeat = 0;
    int column_repeat = 0;
 
    // Iterate over the matrix
    for(int i = 0; i < N; i++)
    {
        for(int j = 0; j < N; j++)
        {
             
            // If current element is
            // present in the main diagonal
            if (i == j)
            {
                 
                // Update trace
                trace += M[i, j];
            }
        }
 
        int flag1 = 0;
 
        // Iterate over each row
        // and increment row_repeat
        // if repeated values exists
        for(int j = 0; j < N; j++)
        {
            for(int k = 0; k < N; k++)
            {
                 
                // For each valid range
                if (j != k && M[i, j] == M[i, k])
                {
                    row_repeat++;
                    flag1 = 1;
                    break;
                }
            }
 
            if (flag1 == 1)
            {
                break;
            }
        }
 
        int flag2 = 0;
 
        // Iterate over each column and
        // increment column_repeat if
        // repeated values are encountered
        for(int j = 0; j < N; j++)
        {
            for(int k = 0; k < N; k++)
            {
                 
                // For each valid range
                if (j != k && M[j, i] == M[k, i])
                {
                    column_repeat++;
                    flag2 = 1;
                    break;
                }
            }
 
            if (flag2 == 1)
            {
                break;
            }
        }
    }
 
    // Answer
    string output = trace + " " + row_repeat + " " +
                    column_repeat + "\n";
 
    // Return answer
    return output;
}
 
// Driver Code
public static void Main(string[] args)
{
    int[, ] M = { { 1, 2, 3, 4 },
                  { 2, 1, 4, 3 },
                  { 3, 4, 1, 2 },
                  { 4, 3, 2, 1 } };
    int N = M.GetLength(0);
 
    string output = vestigium(N, M);
 
    // Print the output
    Console.Write(output);
}
}
 
// This code is contributed by ukasp

Javascript




<script>
// javascript program for the above approach
 
// Function to calculate trace of
// a matrix and number of rows and
// columns with repeated elements
function vestigium( N , M)
{
    // Stores the trace, number of
    // rows and columns consisting
    // of repeated matrix elements
    var trace = 0, row_repeat = 0;
    var column_repeat = 0;
 
    // Iterate over the matrix
    for (i = 0; i < N; i++) {
 
        for (j = 0; j < N; j++) {
 
            // If current element is
            // present in the main diagonal
            if (i == j) {
 
                // Update trace
                trace += M[i][j];
            }
        }
 
        var flag1 = 0;
 
        // Iterate over each row
        // and increment row_repeat
        // if repeated values exists
        for (j = 0; j < N; j++) {
            for (k = 0; k < N; k++) {
 
                // For each valid range
                if (j != k
                    && M[i][j] == M[i][k]) {
                    row_repeat++;
                    flag1 = 1;
                    break;
                }
            }
 
            if (flag1 == 1) {
 
                break;
            }
        }
 
        var flag2 = 0;
 
        // Iterate over each column and
        // increment column_repeat if
        // repeated values are encountered
        for (j = 0; j < N; j++) {
            for (k = 0; k < N; k++) {
 
                // For each valid range
                if (j != k
                    && M[j][i] == M[k][i]) {
 
                    column_repeat++;
                    flag2 = 1;
                    break;
                }
            }
 
            if (flag2 == 1) {
 
                break;
            }
        }
    }
 
    // Answer
    var output = trace + " "
                    + row_repeat + " "
                    + column_repeat + "\n";
 
    // Return answer
    return output;
}
 
// Driver Code
    var M = [ [ 1, 2, 3, 4 ],
                  [ 2, 1, 4, 3 ],
                  [ 3, 4, 1, 2 ],
                  [ 4, 3, 2, 1 ] ];
    var N = M.length;
 
    var output = vestigium(N, M);
 
    // Prvar the output
    document.write(output);
 
 
// This code contributed by shikhasingrajput
 
</script>
Output: 
4 0 0

 

Time Complexity: O(N3)
Auxiliary Space: O(N2)

 

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