Solutions to Homework Assignment 3
Solutions to Homework Assignment 3
Here are my solutions to homework 3. Please let me know if you find an error!
Problem 9.1 in Austin/Chancogne.
The abbreviated solution is:
/*
* ======================================================================
* prog_quadratic4.c : This is Problem 9.1 in book.
*
* Solve Quadratic Equations : Coefficients are read in from keyboard
* : Roots of Quadratic are printed to screen.
*
* Note : Algorithm takes into account possible loss of accuracy when
* two floating point numbers of almost equal size are subtracted.
* ======================================================================
*/
#include <stdio.h> /* Standard Input/Output function declarations */
#include <math.h> /* Math functions, such as sqrt(x). */
#include <stdlib.h> /* Declaration for exit(1). */
float discriminant( float , float , float );
int mySign( float );
void readCoefficients ( float *, float *, float * );
int main( void ) {
float fA, fB, fC; /* Coefficients for Quadratic Equation */
float fRoot1, fRoot2; /* Real Roots 1 and 2 of Quadratic Equation */
float fDiscriminant; /* Discriminant of Quadratic */
float fQ; /* Quotient for Numerical Algorithm */
char caBuffer[8]; /* Buffer array to hold input from screen */
/* [a] : Print Welcome Message */
printf("Welcome to the Quadratic Equation Solver (Version 1)\n");
printf("====================================================\n");
/* [b] : Read in Set of Equations */
printf("\nWould you like to input a quadratic quations (yes/no/quit) ? ");
scanf("%s%*c", caBuffer);
if(strcmp(caBuffer,"yes") != 0)
exit (1);
/* [c] : Read coefficients from the keyboard */
readCoefficients ( &fA, &fB, &fC );
/* [d] : Print Quadratic Equation to Screen */
printf("Equation you have entered is : %g.x^2 + %g.x + %g\n", fA, fB, fC);
/* [e] : Compute Roots of simplified equations : fA equals zero */
.... details are the same as in the book ....
/* [f] : Compute Roots of Quadratic Equation : fA not equal to zero */
.... details are the same as in the book ....
}
/*
* ===================================================
* Function to compute sign of a floating point number
* ===================================================
*/
int mySign( float fX ) {
.... details are the same as in the book ....
}
/*
* ======================================================
* Function to Compute Discriminant of Quadratic Equation
* ======================================================
*/
float discriminant( float dA, float dB, float dC ) {
return(dB*dB - 4.0*dA*dC);
}
/*
* ======================================================
* readCoefficients () -- read coefficients from keyboard.
*
* Input : float *fpA -- Pointer to Coefficient "a".
* : float *fpB -- Pointer to Coefficient "b".
* : float *fpC -- Pointer to Coefficient "c".
* Output : void.
* ======================================================
*/
void readCoefficients ( float *fpA, float *fpB, float *fpC ) {
printf("Please enter coefficients for equation a.x^2 + b.x + c\n");
printf("Enter coefficient a : ");
scanf("%f%*c", fpA );
printf("Enter coefficient b : ");
scanf("%f%*c", fpB );
printf("Enter coefficient c : ");
scanf("%f%*c", fpC );
}
Problem 9.2 in Austin/Chancogne.
/*
* ======================================================================
* prog_countblanks.c : Count blanks in character string.
*
* Written By : Mark Austin March 1998
* ======================================================================
*/
#include <stdio.h> /* Standard Input/Output function declarations */
#include <math.h> /* Math functions, such as sqrt(x). */
int countblanks( char * );
int main( void ) {
char caMessage [] = "This string contains four blanks";
printf("The test string is : \"%s\"\n", caMessage );
printf("It contains %d blanks \n", countblanks( caMessage ));
}
/*
* ====================================================================
* countblanks() : Count number of blanks in a character string.
*
* Input : char *cpString -- pointer to character string.
* Output : int -- number of blanks in the character string.
* ====================================================================
*/
int countblanks( char *cpString ) {
int ii, iNoBlanks = 0;
ii = 0;
while ( cpString[ii] != '\0' ) {
if ( cpString[ii] == ' ' ) {
iNoBlanks = iNoBlanks + 1;
}
ii = ii + 1;
}
return ( iNoBlanks );
}
Example. The output generated by the executable program BLANKS is:
prompt >> BLANKS The test string is : "This string contains four blanks" It contains 4 blanks prompt >>
Problem 9.3 in Austin/Chancogne.
/*
* ===============================================================
* Convert date from an integer to character string representation
*
* Written By : Mark Austin April 1998
* ===============================================================
*/
#include <stdio.h>
#include <stdlib.h>
/* Function declaration */
void DateToString( char *, int, int, int );
/*
* ==============================
* Test Program
* ==============================
*/
int main( void ) {
enum { LengthOfDate = 50 }; /* Length of array for date */
char caDate[ LengthOfDate ]; /* Character array for the date */
DateToString( caDate, 25, 12, 1998 );
printf("Christmas Day is : %s \n", caDate );
DateToString( caDate, 29, 2, 2000 );
printf("Last Day in February, 2000 is : %s \n", caDate );
DateToString( caDate, 31, 4, 1998 );
printf("Last Day in April, 1998 is : %s \n", caDate );
}
/*
* ======================================================================
* DateToString() : Convert integer representation of date into character
* string.
*
* Input : char * -- Pointer to character string array.
* : int iDay -- Day.
* : int iMonth -- Month.
* : int iYear -- Year.
* Output : void.
* ======================================================================
*/
void DateToString( char *cpDate , int iDay, int iMonth, int iYear ) {
int iaNoDaysInMonth[ 12 ] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
char *cpMonth[] = { "January", "February", "March", "April",
"May", "June", "July", "August",
"September", "October", "November", "December" };
char caDay[8];
/* Check that "month" falls within defined ranges */
if( iMonth < 1 || iMonth > 12 ) {
printf("Error : Month should be in range 1 through 12 i\n");
exit(1);
}
/* Check that "day" falls within defined ranges */
if( iYear%4 == 0 )
iaNoDaysInMonth[ 1 ] = 29;
if(iDay < 1 || iDay > iaNoDaysInMonth [ iMonth - 1 ] ) {
printf("Error : There are only %3d days in %s\n",
iaNoDaysInMonth [ iMonth - 1 ], cpMonth [ iMonth-1 ] );
exit(1);
}
/* Build character array containing date */
sprintf (caDay,"%2d", iDay);
strcpy (cpDate, caDay );
strcat (cpDate, "-");
strcat (cpDate, cpMonth[ iMonth-1 ]);
strcat (cpDate, "-");
sprintf (caDay,"%2d", iYear);
strcat (cpDate, caDay );
}
Example. Here is the program output:
prompt >> DATETOSTRING Christmas Day is : 25-December-1998 Last Day in February, 2000 is : 29-February-2000 Error : There are only 30 days in April prompt >>
Developed in February 2000 by Mark Austin
Copyright © 2000, Departments of Civil and Mechanical Engineering, University of Maryland