算法：如何查找矩阵中每一列的最大元素？

本文概述

• C ++
• Java
• Python3
• C#
• 的PHP

给定一个矩阵, 任务是找到每一列的最大元素。

例子：

Input:  [1, 2, 3]
         [1, 4, 9]
         [76, 34, 21]

Output:
76
34
21

Input: [1, 2, 3, 21]
        [12, 1, 65, 9]
        [1, 56, 34, 2]
Output:
12
56
65
21

方法：

这个想法是为no_of_cols运行循环。检查列中的每个元素并查找最大元素。最后, 打印元素。

下面是上述方法的实现：

C ++

// C++ program to find the maximum
// element of each column.
#include <bits/stdc++.h>
using namespace std;
const int MAX = 100;
  
// Function to find the maximum
// element of each column.
void largestInColumn( int mat[][MAX], int rows, int cols)
{
     for ( int i = 0; i < cols; i++) {
         // initialize the maximum element
         // with 0
         int maxm = mat[0][i];
  
         // Run the inner loop for rows
         for ( int j = 1; j < rows; j++) {
             // check if any element is greater 
             // than the maximum element
             // of the column and replace it
             if (mat[j][i] > maxm)
                 maxm = mat[j][i];
         }
  
         // print the largest element of the column
         cout << maxm << endl;
     }
}
  
// Driver code
int main()
{
     int n = 4, m = 4;
     int mat[][MAX] = { { 3, 4, 1, 8 }, { 1, 4, 9, 11 }, { 76, 34, 21, 1 }, { 2, 1, 4, 5 } };
  
     largestInColumn(mat, n, m);
  
     return 0;
}

Java

// Java program to find maximum
// element of each column in a matrix
public class GFG {
  
     // Function to find the maximum
     // element of each column.
     public static void largestInColumn( int cols, int [][] arr)
     {
  
         for ( int i = 0 ; i < cols; i++) {
  
             // Initialize max to 0 at beginning
             // of finding max element of each column
             int maxm = arr[ 0 ][i];
             for ( int j = 1 ; j < arr[i].length; j++)
                 if (arr[j][i] > maxm)
                     maxm = arr[j][i];
  
             System.out.println(maxm);
         }
     }
  
     // Driver code
     public static void main(String[] args)
     {
         int [][] arr = new int [][] { { 3 , 4 , 1 , 8 }, { 1 , 4 , 9 , 11 }, { 76 , 34 , 21 , 1 }, { 2 , 1 , 4 , 5 } };
         // Calling the function
         largestInColumn( 4 , arr);
     }
}

Python3

# Python3 program to find the maximum 
# element of each column
MAX = 100
  
# function to find the maximum
# elements of each column
def largestInColumn(mat, rows, cols):
     for i in range (cols):
          
         # initialize the maximum element with 0
         maxm = mat[ 0 ][i]
         # run the inner loop for news
         for j in range (rows):
              
             # check if any elements is greater 
             # than the maximum elements
             # of the cloumn and replace it
             if mat[j][i] > maxm:
                 maxm = mat[j][i]
          
         # print the largest element
         # of the column
         print (maxm)
  
# Driver code
n, m = 4 , 4
mat = [[ 3 , 4 , 1 , 8 ], [ 1 , 4 , 9 , 11 ], [ 76 , 34 , 21 , 1 ], [ 2 , 1 , 4 , 5 ]]
      
largestInColumn(mat, n, m); 
  
# This code is contributed 
# by Mohit kumar 29 (IIIT gwalior)

C#

// C# program to find maximum
// element of each column in a matrix
using System;
  
class GFG 
{
  
// Function to find the maximum
// element of each column.
public static void largestInColumn( int cols, int [, ] arr)
{
     for ( int i = 0; i < cols; i++)
     {
  
         // Initialize max to 0 at beginning
         // of finding max element of each column
         int maxm = arr[0, i];
         for ( int j = 1; j < arr.GetLength(0); j++)
             if (arr[j, i] > maxm)
                 maxm = arr[j, i];
  
         Console.WriteLine(maxm);
     }
}
  
// Driver code
public static void Main()
{
     int [, ] arr = new int [, ] { { 3, 4, 1, 8 }, { 1, 4, 9, 11 }, { 76, 34, 21, 1 }, { 2, 1, 4, 5 } };
     // Calling the function
     largestInColumn(4, arr);
}
}
  
// This code is contributed 
// by Akanksha Rai

的PHP

<?php
// PHP program to find the maximum 
// element of each column. 
$MAX = 100; 
  
// Function to find the maximum 
// element of each column. 
function largestInColumn( $mat , $rows , $cols ) 
{ 
     for ( $i = 0; $i < $cols ; $i ++) 
     { 
         // initialize the maximum element 
         // with 0 
         $maxm = $mat [0][ $i ]; 
  
         // Run the inner loop for rows 
         for ( $j = 1; $j < $rows ; $j ++)
         { 
             // check if any element is greater 
             // than the maximum element 
             // of the column and replace it 
             if ( $mat [ $j ][ $i ] > $maxm ) 
                 $maxm = $mat [ $j ][ $i ]; 
         } 
  
         // print the largest element 
         // of the column 
         echo $maxm , "\n" ; 
     } 
} 
  
// Driver code 
$n = 4;
$m = 4; 
$mat = array ( array ( 3, 4, 1, 8 ), array ( 1, 4, 9, 11 ), array ( 76, 34, 21, 1 ), array ( 2, 1, 4, 5 )); 
  
largestInColumn( $mat , $n , $m ); 
  
// This code is contributed by Sach_Code
?>

输出如下：

76
34
21
11

时间复杂度：O(n * m), 这里n是矩阵的行数, m是矩阵的列数。

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