Finding min and max in 2-D arrays? - c++

Question

After running this code , it will generate a random array of desired rows and columns . Then a loop will divide the array by its diagonal into an upper side and lower side.In the upper side the loop will look for a max number and in the lower side the loop will look for a min number . Then in the final stage I need to change the positions of min and max . Max in place of min and vice versa.The code runs and finds the min and max.Don't know how to change their places.
Code
#include <iostream>
#include <time.h>
#include <limits.h>
using namespace std;
int main(){
int rows, columns;
int max = INT_MAX;
int min = INT_MIN;
int XindexOfMax, YindexOfMax;
int XindexOfMin, YindexOfMin;
cout << "Enter rows: ";
cin >> rows;
cout << "Enter columns: ";
cin >> columns;
int **array = new int *[rows]; //generating random array
for(int i = 0; i < rows; i++)
array[i] = new int[columns];
srand((unsigned int)time(NULL)); //generating randoms
for(int i = 0; i < rows; i++){ //loop for the main array
for(int j = 0; j < columns; j++){
array[i][j] = rand() % 10;
cout << array[i][j] << " ";
}
cout << "\n";
}
cout << "For finding Max: " << endl;
for(int i = 0; i < rows; i++){ //upper half of the diagonal
for(int j = 0; j < columns - i; j++){
cout << array[i][j] << " ";
if(array[i][j] > max){
max = array[i][j];
XindexOfMax = i; //find x and y coordinates if max
YindexOfMax = j;
}
}
cout << "\n";
}
cout << "For finding Min: " << endl;
for (int i = 0; i < rows; i++){ // lower half of the diagonal
for (int j = 0; j < columns; j++){
if (j < columns - i - 1){
cout << " ";
}
else{
cout << array[i][j] << " ";
if(array[i][j] < min){
min = array[i][j];
XindexOfMin = i; //find x and y coordinates if min
YindexOfMin = j;
}
}
}
cout << "\n";
}
cout << "Result" << endl;
//swapping positions of min and max
std::swap(array[XindexOfMax][YindexOfMax], array[XindexOfMin][YindexOfMin]);
for(int i = 0; i < rows; i++){
for(int j = 0; j < columns; j++){
cout << array[i][j] << " "; //Printing the final array
}
cout << "\n";
}
return 0;
}

Answer 1

In addition to the min and max values, you need to remember the indizes where you found min and max, respectively. Then you can exchange the values (either manually or by using std::swap).
BTW: you need to initialize max and min with INT_MIN and INT_MAX, respectively, and not the other way around.
So it needs to be
int max = INT_MIN;
int min = INT_MAX;
Otherwise, if you write int max = INT_MAX, then no comparison like if(array[i][j] > max) will ever evaluate to true, since there is no integral value greater than INT_MAX.

Answer 2

The swapping is done at the end of main() using std::swap().
I broke a couple of routines into functions. The answer would be improved by breaking out more functions so that each function performs a single task. Still, I added a class, yet tried to stay true to your original design for printing the triangle halves. Hope you can handle some classes at this point.
#include <iostream>
#include <time.h>
#include <limits.h>
#include <cmath>
using namespace std;
class Point {
public:
Point(int x, int y, int value) : x(x), y(y), value(value) {}
int X() { return x; }
int Y() { return y; }
int Value() { return value; }
void SetValue(int valueArg) { value = valueArg; }
void SetPoint(int xArg, int yArg, int valueArg) {
x = xArg;
y = yArg;
value = valueArg;
}
string to_string() {
return std::to_string(value);
}
private:
int x;
int y;
int value;
};
void PrintArray(int **array, int rows, int columns) {
for (int i = 0; i < rows; i++) {
for (int j = 0; j < columns; j++) {
cout << array[i][j] << " ";
}
cout << "\n";
}
}
int main() {
int rows, columns;
cout << "Enter rows: ";
cin >> rows;
cout << "Enter columns: ";
cin >> columns;
int **array = new int *[rows]; //generating random array
for (int i = 0; i < rows; i++)
array[i] = new int[columns];
srand((unsigned int) time(NULL));
for (int i = 0; i < rows; i++) {
for (int j = 0; j < columns; j++) {
array[i][j] = rand() % 10; //generating randoms
}
}
PrintArray(array, rows, columns);
Point maxPoint = Point(0, 0, INT_MIN); // initialize max
Point minPoint = Point(0, 0, INT_MAX);;
cout << "For finding Max: " << endl;
for (int i = 0; i < rows; i++) { //separating the upper half
for (int j = 0; j < columns - i; j++) {
if (j > columns - i) {
cout << array[i][j] << " ";
} else {
cout << array[i][j] << " ";
if (array[i][j] > maxPoint.Value()) {
maxPoint.SetPoint(i, j, array[i][j]);
}
}
}
cout << "\n";
}
cout << "For finding Min: " << endl;
for (int i = 0; i < rows; i++) { //separating the lower half
for (int j = 0; j < columns; j++) {
if (j < columns - i - 1) {
cout << " ";
} else {
cout << array[i][j] << " ";
if (array[i][j] < minPoint.Value()) {
minPoint.SetPoint(i, j, array[i][j]);
}
}
}
cout << "\n";
}
cout << "array before: " << endl;
PrintArray(array, rows, columns);
cout << "Swapping " << "maxPoint(" << maxPoint.X() << ", " <<
maxPoint.Y() << ") with minPoint("
<< minPoint.X() << ", " << minPoint.Y() << ")" << endl;
std::swap(
minPoint.GetCellReference(array),
maxPoint.GetCellReference(array));
PrintArray(array, rows, columns);
return 0;
}
As mentioned in one of the comments, std::swap() is one method of performing a swap. I have modified the example to use std:swap() at the end of main();