[Add] completed projects

Project/4/main.cpp

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+#include <stdio.h>
+#include <assert.h>
+void DrawSpiralLine(const int n, const int line)
+{
+    // Throw an assertion when faulty parameters are supplied.
+    assert(line >= 0 && line < n && n > 0);
+    const int square = n * n;
+    int       i      = 0;
+    // Simple case: The first line of a spiral.
+    if (line == 0)
+    {
+        for (i = 0; i < n; i++)
+        {
+            printf("%02d ", (square - 1) - i);
+        }
+    }
+    // Simple case: The last line of a spiral.
+    else if (line == (n - 1))
+    {
+        for (i = 0; i < n; i++)
+        {
+            printf("%02d ", square - (3 * n) + 2 + i);
+        }
+    }
+    // Complex case: Line with other inner spirals.
+    else
+    {
+        // Print the first character.
+        printf("%02d ", square - (4 * n) + 4 + (line - 1));
+        // Print a line of the rest
+        DrawSpiralLine(n - 2, line - 1);
+        // Print the last character
+        printf("%02d ", (square - 1) - n - (line - 1));
+    }
+}
+void DrawSpiral(const int n)
+{
+    int i = 0;
+    // Draw the lines of the spiral.
+    for (i = 0; i < n; i++)
+    {
+        DrawSpiralLine(n, i);
+        printf("\n");
+    }
+}
+int main(void)
+{
+    DrawSpiral(5);
+    printf("\n");
+    DrawSpiralLine(6, 2);
+    return 0;
+}