The classic Palindrome problem

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

int isPalindrome( char *s );

int main ( void )
{
   int i = 0;
   int ch;
   char s[100];
 
   while ((ch = getchar()) != ('\n')) {
      if (isalpha(ch)) {
         ch = toupper(ch);
         s[i] = ch;
         i++;
      }
   }
   s[i]='\0';
 
   if ( isPalindrome(s) == 1) {
      printf("Yes, it is a palindrome.\n");
   } else {
      printf("No, it is not a palindrome.\n");
   }
 
   getchar();  
   return 0;
 
}
 
int isPalindrome( char *s )
{
   int i = strlen(s)-1;
   int j = 0;
 
   while (j < i) {
      if(s[j] != s[i]) {
         return 0;
      }
      i--;
      j++;
   }
   return 1;
}

A good video to review OOP concepts

From www.youtube.com

The classic "atoi" question

//Language C++
#include <iostream>
using namespace std;

int atoi(char *s)
{
  int i=0;
  while(*s)
  {
    if (*s ==' ' || *s =='\t')
       s++;
    else {
    if ( *s < '0' || *s > '9' )
         return i;  
    i = i*10 + (*s- '0');
    s++;
    }
  }
  return i;
}

int my_atoi(char* pStr) {

    if (pStr == NULL) {
        printf("ERROR: null string.\n");
        return -1;
    }

    int num = 0;

    int pos;
    for (pos = 0; ; pos++) {
        char currChar = *(pStr+pos);

        // Check whether the current char is not a digit
        if ( currChar < '0' || currChar > '9' )
            return num;

        // Read the number and add it to the 'num' variable
        num = (num*10) + (int) currChar - (int)'0';
    }
    return num;
}

int s_atoi(char *s)
{
  int i = 0;
  while(*s)
  {
    if ( *s < '0' || *s > '9' )
         return i;
    i = (i<<3) + (i<<1) + (*s - '0');
    cout <<i <<endl;
    s++;
  }
  return i;
}

/////////////
int Atoi(const char *pstr)
{
int sign = 1;
int num = 0;
while (*pstr == ' ' || *pstr == '\t')
{
pstr++;
}
if (*pstr == '-')
{
sign = -1;
pstr++;
}
while (*pstr)
{
if (*pstr >= '0' && *pstr <= '9')
{
num = 10 * num + *pstr - '0';
}
else
{
return num * sign;
}
pstr++;
}
return (num * sign);
}
//////////////

int main(){
char *s = "  9885 pigs";
cout << atoi(s) <<endl;
getchar();
cout << my_atoi(s) <<endl;
getchar();
cout << s_atoi(s) <<endl;
getchar();
cout << Atoi(s) <<endl;
getchar();
cout<<"-----ascii----"<<endl;
for(char ch = 'A'; ch <= 'Z'; ch++)
//insert cout statement here, as clearly your professor wont like
    printf("%x %i %c \n" , ch,ch,ch);
    getchar();
return 0;
}

Warm up question: What is the difference between Hashtable and Hashmap?

Notes on Hashtable and Hashmap.

      Both provide key-value access to data.

• HashMap permits null value while Hashtable does not.
• Access to Hashtable is synchronized on the table while access to the HashMap is not (by default).
• Iterator in the HashMap is fail-safe while the enumerator for the Hashtable is not.
• Hashtable is an original collection class in Java while HashMap is part of the new collections framework.

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