/*
**    Source:  sqrt.c  
**    Author:  Scott Wenger 1997 
**             Box 802
**             Stevens Point, WI 54481
**             panther@wctc.net

**   Purpose:  approximation of square root 

**             This program uses standard header files.  If your
**             compiler requires other header files to handle floating
**             point, use the appropriate header files  and / or
**             library for your compiler.  
*/


#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <conio.h>


// function prototypes
float s_root(int number);
int validate(char input[]);
void prim_cls();


//  s_root calculates approximate square root

float s_root(int number)
{
  register int x = 1;
  float q;
  float sr;
  float avg;
  int z = 1;
  char buffer[20];
  int i = 0;
    
  do {
    z++;  
    if (z * z == number) 
      return( (float) z);  // found the square root (a whole number) 
  } while (z * z < number);

  // if still in function, compute the fractional square root... 
    
  while(x * x < number) x++;
	  
  q = (float) number / x;
  sprintf(buffer, "%.1f", q);
  sr =  (float) atof(buffer);
  avg = (float) .5 * (x + sr);
  
  for (i = 0; i < 3; i++) {    // get closer approximation 
    q = number / avg;
    avg = (float) .5 * (avg + q);
    q = number / avg;
  }  
  return(q);  
}

/*--------------------------------------------------------------*/

int validate(char input[])
{
  int valid = 1;  
  register int i;
  int len = strlen(input);

  if (len > 4) return(0);

  if ( *(input + len - 1) == '\n') *(input + len - 1) = '\0';
    
  for (i = 0; i < len; i++) {
    if ( *(input + i) < '0' || *(input + i) > '9')
      valid = 0;      
  }
  return(valid);
} 

/*--------------------------------------------------------------*/

void prim_cls()
{
  register int i;	
  for (i = 0; i < 80; i++) printf("\n");
}

/*--------------------------------------------------------------*/

main()
{
  int   question;
  int   valid = 0;
  int   retval = 1;
  int   decision;
  char  input[500];
  char  more;
  float answer;
  
  while (!valid) {
    prim_cls();	 
    if (!retval) {
      printf("\nInvalid entry.");
      printf("\nTry again.\n\n");
      retval = 1;
    }	    
    printf("\nEnter an integer (1 to 9999):  ");
    fflush(stdout);
    scanf("%s", input);
    retval = validate(input);    
    if (!retval) {
      continue;
    }	    
    question = atoi(input);  
    answer = s_root(question);
    printf("\nApproximate square root of %d is %f\n\n", question, answer);

    decision = 0; 
    printf("\nContinue ? (y or n): [ ]\b\b");
    fflush(stdout);
    while (!decision) {
      more = getch();
      if (more == 'y' || more == 'Y') decision = 1;
      if (more == 'n' || more == 'N') {
        printf("\n\n");	      
        exit(0);     
      }        
    }    
  }    
}

/*--------------------------------------------------------------*/