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Count all the columns in a matrix which are sorted in descending

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Given a matrix mat[][], the task is to count the number of columns that are sorted in descending. 

Examples:

Input: mat[][] = {{1, 3}, {0, 2}} 
Output: 2 First column: 1 > 0 Second column: 3 > 2 Hence, the count is 2 

Input: mat[][] = {{2, 2}, {1, 3}} 
Output: 1

Approach: 

Traverse each column one by one and check if the next element ? previous element in the same column. If the condition is valid for all the possible elements then increment the count by 1. After all the columns have been traversed, print the count

Below is the implementation of the above approach: 

C++




#include <iostream>
#include <vector>
using namespace std;
 
// Function to count the number of columns
// in a matrix that are sorted in descending
int countDescCol(vector<vector<int>> A) {
    int countOfCol = 0;
 
    for (int j = 0; j < A[0].size(); j++) {
        bool isDescending = true;
        for (int i = 0; i < A.size() - 1; i++) {
            if (A[i][j] < A[i + 1][j]) {
                isDescending = false;
                break;
            }
        }
        if (isDescending) {
            countOfCol++;
        }
    }
 
    return countOfCol;
}
 
// Driver code
int main() {
    vector<vector<int>> A = {{1, 3}, {0, 2}};
    cout << countDescCol(A) << endl;
    return 0;
}


Java




// Java code to count the number of columns in
// a matrix that are sorted in descending
import java.util.ArrayList;
import java.util.List;
 
public class Main {
    public static int countDescCol(List<List<Integer>> A) {
        int countOfCol = 0;
 
        for (int j = 0; j < A.get(0).size(); j++) {
            boolean isDescending = true;
            for (int i = 0; i < A.size() - 1; i++) {
                if (A.get(i).get(j) < A.get(i + 1).get(j)) {
                    isDescending = false;
                    break;
                }
            }
            if (isDescending) {
                countOfCol++;
            }
        }
 
        return countOfCol;
    }
 
    public static void main(String[] args) {
        List<List<Integer>> A = new ArrayList<>();
        A.add(new ArrayList<Integer>() {{
            add(1);
            add(3);
        }});
        A.add(new ArrayList<Integer>() {{
            add(0);
            add(2);
        }});
        System.out.println(countDescCol(A));
    }
}


Python3




# Python3 program to count the number of columns
# in a matrix that are sorted in descending
 
# Function to count the number of columns
# in a matrix that are sorted in descending
def countDescCol(A):
   
    countOfCol = 0
   
    for col in zip(*A):
        if all(col[i] >= col[i + 1] for i in range(len(col) - 1)):
            countOfCol += 1
   
    return countOfCol
   
# Driver code
A = [[1, 3], [0, 2]]
print(countDescCol(A))


C#




// Java code to count the number of columns in
// a matrix that are sorted in descending
using System;
using System.Collections.Generic;
 
public class MainClass {
    public static int countDescCol(List<List<int>> A) {
        int countOfCol = 0;
 
        for (int j = 0; j < A[0].Count; j++) {
            bool isDescending = true;
            for (int i = 0; i < A.Count - 1; i++) {
                if (A[i][j] < A[i + 1][j]) {
                    isDescending = false;
                    break;
                }
            }
            if (isDescending) {
                countOfCol++;
            }
        }
 
        return countOfCol;
    }
 
    public static void Main() {
        List<List<int>> A = new List<List<int>>();
        A.Add(new List<int> {1, 3});
        A.Add(new List<int> {0, 2});
        Console.WriteLine(countDescCol(A));
    }
}


Javascript




// Function to count the number of columns in
// a matrix that are sorted in descending order
function countDescCol(A) {
    let countOfCol = 0;
     
    // Transpose the matrix and iterate over its rows (original columns)
    A[0].map((_, colIndex) => A.map(row => row[colIndex])).forEach(col => {
        // Check if the column is sorted in descending order
        if (col.slice(1).every((item, i) => col[i] >= item)) {
            countOfCol += 1;
        }
    });
    return countOfCol;
}
 
// Driver code
let A = [[1, 3], [0, 2]];
console.log(countDescCol(A));


Output

2


Last Updated : 14 Apr, 2023
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