Magic squares of singly even order: Difference between revisions
Magic squares of singly even order (view source)
Revision as of 12:29, 15 November 2017
, 6 years agoAdded C implementation.
(Strachey method in J) |
(Added C implementation.) |
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=={{header|C}}==
<lang C>
/*Abhishek Ghosh, 15th November 2017*/
#include<stdlib.h>
#include<ctype.h>
#include<stdio.h>
int** oddMagicSquare(int n) {
if (n < 3 || n % 2 == 0)
return NULL;
int value = 0;
int squareSize = n * n;
int c = n / 2, r = 0,i;
int** result = (int**)malloc(n*sizeof(int*));
for(i=0;i<n;i++)
result[i] = (int*)malloc(n*sizeof(int));
while (++value <= squareSize) {
result[r][c] = value;
if (r == 0) {
if (c == n - 1) {
r++;
} else {
r = n - 1;
c++;
}
} else if (c == n - 1) {
r--;
c = 0;
} else if (result[r - 1][c + 1] == 0) {
r--;
c++;
} else {
r++;
}
}
return result;
}
int** singlyEvenMagicSquare(int n) {
if (n < 6 || (n - 2) % 4 != 0)
return NULL;
int size = n * n;
int halfN = n / 2;
int subGridSize = size / 4, i;
int** subGrid = oddMagicSquare(halfN);
int gridFactors[] = {0, 2, 3, 1};
int** result = (int**)malloc(n*sizeof(int*));
for(i=0;i<n;i++)
result[i] = (int*)malloc(n*sizeof(int));
for (int r = 0; r < n; r++) {
for (int c = 0; c < n; c++) {
int grid = (r / halfN) * 2 + (c / halfN);
result[r][c] = subGrid[r % halfN][c % halfN];
result[r][c] += gridFactors[grid] * subGridSize;
}
}
int nColsLeft = halfN / 2;
int nColsRight = nColsLeft - 1;
for (int r = 0; r < halfN; r++)
for (int c = 0; c < n; c++) {
if (c < nColsLeft || c >= n - nColsRight
|| (c == nColsLeft && r == nColsLeft)) {
if (c == 0 && r == nColsLeft)
continue;
int tmp = result[r][c];
result[r][c] = result[r + halfN][c];
result[r + halfN][c] = tmp;
}
}
return result;
}
int numDigits(int n){
int count = 1;
while(n>=10){
n /= 10;
count++;
}
return count;
}
void printMagicSquare(int** square,int rows){
int i,j;
for(i=0;i<rows;i++){
for(j=0;j<rows;j++){
printf("%*s%d",rows - numDigits(square[i][j]),"",square[i][j]);
}
printf("\n");
}
printf("\nMagic constant: %d ", (rows * rows + 1) * rows / 2);
}
int main(int argC,char* argV[])
{
int n;
if(argC!=2||isdigit(argV[1][0])==0)
printf("Usage : %s <integer specifying rows in magic square>",argV[0]);
else{
n = atoi(argV[1]);
printMagicSquare(singlyEvenMagicSquare(n),n);
}
return 0;
}
</lang>
Output:
<pre>
35 1 6 26 19 24
3 32 7 21 23 25
31 9 2 22 27 20
8 28 33 17 10 15
30 5 34 12 14 16
4 36 29 13 18 11
Magic constant: 111
</pre>
=={{header|C++}}==
<lang cpp>
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