Initial commit of lecture code

LC17/Quadratic_with_Pointers.c

@@ -0,0 +1,61 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+
+// This function will return
+//
+//  0   if the equation can be solved,
+//  -1  if it is not a quadratic
+//  -2  if it is complex
+
+int SolveQuadratic ( int a, int b, int c, float *x1, float *x2)
+{
+    int d;
+
+    // If the equations is not a quadratic return -1
+    if ( a == 0 )
+        return (-1);
+
+    // Calculate the value that will be square rooted
+    d = (b*b) - (4*a*c);
+
+    // If less than zero then it would be complex - give up!
+    if ( d < 0 )
+        return (-2);
+
+    // If we got to here we are OK to solve things
+    *x1 = (-b - sqrt(d)) / (2*a);
+    *x2 = (-b + sqrt(d)) / (2*a);
+
+    // This is are 'OK' return value
+    return 0;
+
+}
+
+int main()
+{
+    int A,B,C, r;
+    float X1, X2;
+
+    printf ("Please enter a b & c separated by a space: ");
+
+    scanf("%d %d %d",&A, &B, &C);
+
+    r = SolveQuadratic(A,B,C, &X1, &X2);
+
+    // The value returned lets us know if we have values in X1 and X2 we can use
+    switch (r)
+    {
+    case 0 :
+        printf ("The solutions are %f and %f", X1, X2 );
+        break;
+    case -1 :
+        printf ("The equation provided was not a quadratic" );
+        break;
+    case -2 :
+        printf ("The solutions had complex roots and could not be solved");
+        break;
+    }
+    return 0;
+}