Rotating an NxN array 90 degrees in-place with a transpose and flip operation

gistfile1.cpp

#include <iostream>
#include <cstdio>
 
#define DIM 5
 
void swap(int s[DIM][DIM], int i, int j, int k, int l) {
	char c = s[i][j];
	s[i][j] = s[k][l];
	s[k][l] = c;
}
 
void print_matrix(int s[DIM][DIM]) {
	for(int i=0; i<DIM; ++i) {
		for(int j=0; j<DIM; ++j) 
			printf("%d ", s[i][j]);
		printf("\n");
	}
}
 
void rotate(int s[DIM][DIM]) {
	// perform transpose
	for(int i=0; i<DIM; ++i) 
		for(int j=i+1; j<DIM; ++j) 
			swap(s,i,j,j,i);
 	// perform vertical flip
 	for(int i=0; i<DIM; ++i) 
 		for(int j=0; j<DIM/2; ++j)
 			swap(s,i,j,i,DIM-j-1);
}
 
 
int main() {
 
	// initialize a matrix
	int s[DIM][DIM];
	for(int i=0, k=1; i<DIM; ++i)
		for(int j=0; j<DIM; ++j, ++k)
			s[i][j] = k;
 
	puts("Before:");
	print_matrix(s);
 
	rotate(s);
 
	puts("After:");
	print_matrix(s);
 
	return 0;	
}