old stuff: algorithms

1 files changed, 65 insertions, 0 deletions

diff --git a/algorithms/magic.c b/algorithms/magic.c
new file mode 100644
index 0000000..31e50ea
--- /dev/null
+++ b/algorithms/magic.c
@@ -0,0 +1,65 @@
+#include <stdio.h>
+
+
+/*
+  1...25
+
+  0 0 1 0 0
+  0 0 0 0 0
+  0 0 0 0 0
+  0 0 0 0 0
+  0 0 0 0 0
+*/
+void
+magic(unsigned int n)
+{
+  int a[n][n];
+  unsigned int i, j;
+
+  for(i=0; i<n; i+=1) {
+    for(j=0; j<n; j+=1) {
+      a[i][j] = 0;
+    }
+  }
+
+  int k;
+  int row = n - 1;
+  int col = n / 2;
+  for (k = 1; k <= n * n; ++k) {
+    a[row][col] = k;
+    if (k % n == 0) {
+      --row;
+      if (row < 0)
+        row = n - 1;
+    } else {
+      ++row;
+      if (row == n)
+        row = 0;
+      ++col;
+      if (col == n)
+        col = 0;
+    }
+  }
+
+  for(i=0; i<n; i+=1) {
+    for(j=0; j<n; j+=1) {
+      printf("\t%d\t ",a[i][j]);
+    }
+    printf("\n");
+  }
+}
+
+int main(void)
+{
+  int n = 3;
+
+  if(n%2==0) {
+    printf("n has to be odd\n");
+    exit(1);
+  }
+
+  magic(n);
+
+  return 0;
+}
+