How To find a maximum number in a 2D array?

Answer 1

// Pseudocode

int findMax( int[][] data ) {

// Return if data is empty

if( data.length 0 ) {

return 0;

}

int max = data[0][0];

// Iterate through each element in the array

for( int r = 0; r < data.length; ++r ) {

for( int c = 0; c < data[0].length; ++c ) {

// If we find a value greater than the current max, update max

if( data[r][c] > max ) {

max = data[r][c];

}

}

}

return max;

}

Answer 2

Traverse all of the the array elements and store the index of the highest value encountered during the traversal and store the largest value itself.

Repeatedly shift all remaining values to the left to overwrite the largest value and decrement the upper bound of the array (the last element is unused).

If other occurrences of the largest value exist, locate the next occurrence and shift left to remove them, decrementing the upper bound each time.

Finally, reallocate the array to remove all the unused elements at the end of the array.

The following code demonstrates the procedure outlined above, using a randomly allocated dynamic array with random values. Duplicate values are guaranteed, but not necessarily the largest value.

#include <iostream>

#include <iomanip>

#include <time.h>

using namespace std;

int main()

{

// Seed random number generator.

srand(( unsigned int ) time( NULL ));

// Local variables.

int i = 0;

int index = 0, largest = 0;

// Random elements: 5 to 20.

int elements = rand()%16+5;

int * Array = (int *) calloc(elements, sizeof(int));

// Random values: 1 to 75% of 'elements'

// Duplicate values are guaranteed, but

// not necessarily the largest value.

for( i=0; i<elements; ++i )

Array[i]= rand()%((3*elements)/4)+1;

// Print array:

cout << "Original array: " << endl;

for( i=0; i<elements; ++i )

cout << setw( 4 ) << Array[i];

cout << endl << endl;

// Locate the index largest value:

index = 0;

for( i=0; i<elements; ++i )

if( Array[i] > Array[index] )

index = i;

// Store and show largest value:

largest = Array[ index ];

cout << "Largest value is: " << largest << endl << endl;

// Repeat loop to remove all occurances of largest.

while( index < elements )

{

// Shift elements to the left to close the gap (remove largest value).

for( i=index+1; i<elements; ++i )

Array[i-1] = Array[i];

// Store last index.

i = index;

// Reduce upper bound and invalidate index (exit condition for loop).

index = --elements;

// Locate next occurance of largest (if any).

for( ; i<elements; ++i )

{

if( Array[i] == largest )

{

index = i;

break;

}

}

}

// Shrink array to remove all unused elements.

realloc( Array, elements * sizeof( int ));

// Print array:

cout << "New array:" << endl;

for( i=0; i<elements; ++i )

cout << setw( 4 ) << Array[i];

cout << endl << endl;

// Release memory.

free( Array );

return( 0 );

}