#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <math.h>

#define  MAXREAL  1e40

int   ba,bd;
char  x[40],y[40];
float r;

enum bool {
 TRUE, FALSE
};

char *strrev(const char *s) {
 int i=0, len=strlen(s);

 char *str = NULL;
 if ((str=malloc(strlen(s)+1)) == NULL) {/*cannot allocate memory */
  return NULL;
 }

 while(len)
  str[i++]=s[--len];
 str[i] = '\0';
 return (str);
}

// Convert a number from base b to base 10. The function returns
// FALSE if b not in [2..36] or if string x contains invalid
// characters in base b or if result y is too big.
enum bool DecodeBase(char *x,int b, float *y) {
 int lgth,i,j;
 float mult; char *ch;
 if (b<2 || b>36) {
  printf(" Base must be between 2 and 36 !\n");
  return FALSE;
 }
 *y=0; mult=1.0;
 lgth=strlen(x);
 for (i=0; i<lgth; i++) {
  ch=&x[lgth-i-1];
  if (!isalnum(ch[0])) {
  printf(" Error in input number.\n");
  return FALSE;
  }
  if (*ch<='9')
  j=toupper(*ch)-'0';
  else
   j=toupper(*ch)-'A'+10;
  if (j>=b) return FALSE;
  *y+=mult*j;
  if (mult>MAXREAL/b) return FALSE;
  mult=mult*b;
 }
 return TRUE;
}

//Convert a number from base 10 to base b. The function returns
//FALSE if b not in [2..36] or if string x contains invalid
//characters in base 10 or if number x is too big.
enum bool CodeBase(float x,int b, char *y) {
 int n; char ch[2];
 if (b<2 || b>36) {
  printf(" Base must be between 2 and 36 !\n");
  return FALSE;
 }
 strcpy(y, "");
 while (x>0) {
  n=(int) floor(x - b * (int)(x/b));
  if (n<10) {
   //y=Chr(Ord("0")+n)+y;
   sprintf(ch,"%d",n);
  strcat(y,ch);
  }
  else {
   //y=Chr(Ord("A")+n-10) +y;
   switch(n) {
   case 10: strcat(y,"A"); break;
   case 11: strcat(y,"B"); break;
   case 12: strcat(y,"C"); break;
   case 13: strcat(y,"D"); break;
   case 14: strcat(y,"E"); break;
   case 15: strcat(y,"F"); break;
   case 16: strcat(y,"G"); break;
   case 17: strcat(y,"H"); break;
   case 18: strcat(y,"I"); break;
   case 19: strcat(y,"J"); break;
   case 20: strcat(y,"K"); break;
   case 21: strcat(y,"L"); break;
   case 22: strcat(y,"M"); break;
   case 23: strcat(y,"N"); break;
   case 24: strcat(y,"O"); break;
   case 25: strcat(y,"P"); break;
   case 26: strcat(y,"Q"); break;
   case 27: strcat(y,"R"); break;
   case 28: strcat(y,"S"); break;
   case 29: strcat(y,"T"); break;
   case 30: strcat(y,"U"); break;
   case 31: strcat(y,"V"); break;
   case 32: strcat(y,"W"); break;
   case 33: strcat(y,"X"); break;
   case 34: strcat(y,"Y"); break;
   case 35: strcat(y,"Z");
  }
  }
  x=(float) (int)(x/b);
 }
 y=strrev(y); //string inversion
 return TRUE;
}

int main(void)  {

 int theBaseIWant = 2;
 int theNumber = 40;
 char Output[255];

 // From base 10 -> 2
 if(CodeBase(theNumber, theBaseIWant, Output) == TRUE) {
  puts(Output);
 }
 else {
  puts("WWWHHYY!!");
  return 0;
 }

 // From Base 16(Hex) --> Base 2(Binary)
 float decimal;
 char Input[] = "00FF";
 if(DecodeBase(Input, 16, &decimal) == FALSE) {
  puts("WWWHHYY!!");
  return 0;
 }

 if(CodeBase(decimal, 2, Output) == FALSE) {
  puts("WWWHHYY!!");
  return 0;
 }

 printf("Our decimal: %.2f\n", decimal);

 /* Tested the strrev() function
 char *myWord = "Hello World";
 char WordBackwards[strlen(myWord)+1];

 if(strrev(myWord) != NULL) {
  strcpy(WordBackwards, strrev(myWord));
  puts(WordBackwards);
 }
 else {
  puts("AAHH!!");
 }*/

 /* Original source
 printf("\n BASE CONVERSION\n\n");
 printf(" Start  Base (2 to 36): "); scanf("%d",&bd);
 printf(" Arival Base (2 to 36): "); scanf("%d",&ba);
 strcpy(x,"1");
 while (strcmp(x,"0")!=0) {
  printf("\n Enter number in start base: "); scanf("%s",x);
  if (strcmp(x,"0")!=0) {
   if (DecodeBase(x,bd,&r)) {
   if (CodeBase(r,ba,y))
    printf(" In base %d:  %s\n",ba,y);
   else
    printf(" Error in coding number.\n");
   }
   else
   printf(" Error in decoding number.\n");
  }
 }
 printf("\n\n");*/

 return 0;
}

#include <iostream>
#include <string.h>

using namespace std;

int main()
{
	string output;
	int input, base, counter=0;
	cout << "Please input the number to be converted: ";
	cin >> input;
	cout << "Please input the base to convert to: ";
	cin >> base;
	while (input != 0)
	{
		switch (input % base)
		{
		case 0:
			output += '0';
			break;
		case 1:
			output += '1';
			break;
		case 2:
			output += '2';
			break;
		case 3:
			output += '3';
			break;
		case 4:
			output += '4';
			break;
		case 5:
			output += '5';
			break;
		case 6:
			output += '6';
			break;
		case 7:
			output += '7';
			break;
		case 8:
			output += '8';
			break;
		case 9:
			output += '9';
			break;
		case 10:
			output += 'A';
			break;
		case 11:
			output += 'B';
			break;
		case 12:
			output += 'C';
			break;
		case 13:
			output += 'D';
			break;
		case 14:
			output += 'E';
			break;
		case 15:
			output += 'F';
			break;
		case 16:
			output += 'G';
			break;
		case 17:
			output += 'H';
			break;
		case 18:
			output += 'I';
			break;
		case 19:
			output += 'J';
			break;
		case 20:
			output += 'J';
			break;
		case 21:
			output += 'K';
			break;
		case 22:
			output += 'L';
			break;
		case 23:
			output += 'M';
			break;
		case 24:
			output += 'N';
			break;
		case 25:
			output += 'O';
			break;
		case 26:
			output += 'P';
			break;
		case 27:
			output += 'Q';
			break;
		case 28:
			output += 'R';
			break;
		case 29:
			output += 'S';
			break;
		case 30:
			output += 'T';
			break;
		case 31:
			output += 'U';
			break;
		case 32:
			output += 'V';
			break;
		case 33:
			output += 'W';
			break;
		case 34:
			output += 'X';
			break;
		case 35:
			output += 'Y';
			break;
		case 36:
			output += 'Z';
			break;
		}
		input = input/base;
		counter++;
	}
	cout << "The result of the conversion is ";
	while (counter > -1)
	{
		cout << output[counter];
		counter--;
	}
	cout << "\n";
	return 0;
}

char* strrev(char *str) {
	char *p1, *p2;

	if (!str || !*str)
		return str;

	for (p1 = str, p2 = str + strlen(str) - 1; p2 > p1; ++p1, --p2) {
		*p1 ^= *p2;
		*p2 ^= *p1;
		*p1 ^= *p2;
	}

	return str;
}