DSA-Lecture03-Pointers, Strings(outputs).pptx

Today’s Agenda --
1. Pointers
◦ Chapter 1 DSA 4th
Ed by Adam Drozdek
◦ SlideShare handouts
2. Strings
◦ Chapter 1 DSA 4th
Ed by Adam Drozdek
◦ SlideShare handouts
3. Quiz

Today’s Outline -- Pointers (in C++)
◦Introduction (Recap)
◦Pointer Arithmetic
◦Pointer & Arrays
◦Reference Variables
◦Pointers in Functions
◦New, Delete Function
(Chapter 1 by Adam Drozdek)

Today’s Outline -- Strings (in C++)

Pointer Arithmetic
#include <iostream>
using namespace std;
int main() {
int a=67;
int* p1= &a;
cout<<" original p is address of a " <<p1;
p1++;
cout<<" n now p is next to a like " <<p1;
return 0; }

Pointer Arithmetic contd..
int x= 10;
int *ptr;
ptr= &x;
cout<<ptr<<endl;
cout<<ptr++<<endl;
cout<<ptr;

Pointer Arithmetic contd..
cout<<*ptr<<endl;
cout<<++*ptr<<endl;
cout<<*ptr<<endl;
cout<<*ptr++<<endl;
cout<<*ptr<<endl;
cout<<ptr<<endl;
cout<<*ptr;
cout<<*ptr<<endl;
cout<<(*ptr)++<<endl;
cout<<x<<endl;

Pointers & Arrays
int arr[2]={6,87};
int* p1= &arr[0];
cout<<*p1<<" " <<p1<<endl;
cout <<*arr<<" " <<arr;

int arr[2]={6,87};
int* p1= &arr[0];
cout <<p1 << " " <<*p1;
cout<<" n " << *p1++ <<" " <<*p1;
_______________________________________________________
int arr[2]={6,87};
int* p1= &arr[0];
cout <<p1 << " " <<*p1;
cout<<" n " << (*p1)++ <<" " <<*p1;
Pointers & Arrays contd..

int arr[2]={6,87};
int* p1= &arr[0];
cout <<p1 << " " <<*p1;
cout<<" n " << *++p1 <<" " <<*p1;
_________________________________________________
int arr[2]={6,87};
int* p1= &arr[0];
cout <<p1 << " " <<*p1;
cout<<" n " << ++*p1 <<" " <<*p1;

void scan(int* p, int n)
{ for (int i =0; i<n; i++)
cout<<*(p+i)<<"n";}
int main() {
int arr[4]= {1, 2, 7, 8};
scan(arr, 4);
_______________________________________________
void scan(int* p, int n)
{ for (int i =0; i<n; i++)
cout<<*(p+i)<<"n";
*(p+2)=3;}
int main() { int arr[4]= {1, 2, 7, 8};
scan(arr, 4);
for(int j=0;j<4;j++)
{cout<< arr[j]<<" ";}

Pointers and Strings
char str[]= "computer";
char *ptr= str;
cout<<str<<endl;
cout<<*ptr<<endl;

Array of Pointers
char *ptr[] = { "car", "bus", "bike", "truck"};
cout<<*ptr;
char *ptr[] = { "car", "bus", "bike", "truck"};
cout<<*ptr<<endl;
for(int i=0; i<4; i++)
{ cout<<*ptr[i]<<endl;}

String Class
In C++, you can also create a string object for holding strings.
Unlike using char arrays, string objects has no fixed length, and
can be extended as per your requirement.

12/07/2024 Engr. Kanwal Yousaf 17
String is a sequence of consecutive characters which ends with ‘0’.
String Operations along with the syntax can be:
String Operations
Operations Traditional Syntax
Length Length(string);
Concatenation Concate(string1, string2);
Comparison Compare(string1, string2);
Copy CopyString(string1, string2);
Substring Substring(string, strt_position_int, end_position_int);

Operations Description Example
Length The number of characters in the string LENGTH(‘COMPUTER’)=8,
LENGTH(‘ ’)=?
Concatenation To combine two strings into one. S1=‘Hello’, S2=‘Pakistan’ then
S1 + S2= ‘HelloPakistan’
But
S1+ ‘ ’ + S2= ‘Hello Pakistan’
Comparison To compare any two strings
Returns < 0, if (String 1 < String 2)
Returns =0, if (String1 == String 2)
Returns >0, if (String 1> String 2)
S1=‘Hello’, S2= ‘Pakistan’ then ?
COMPARE(S1, S2)=?
S1=‘Welcome to Java’, S2= ‘Welcome to C’
then
COMPARE(S1, S2)=?
Copy To copy the characters of one string to the
another
S1=‘Data Structures’, S2=‘Algorithms’
Then Copy_String=(S1, S2) = ‘Algorithms’
Substring Display the part of string SUBSTRING(‘The End’, 4, 4)=?
String Operations (Cont…)

Value
Relation between Compared
String and Comparing String
0 They compare equal
<0
Either the value of the first character
that does not match is lower in
the compared string, or all compared
characters match but the compared
string is shorter.
>0
Either the value of the first character
that does not match is greater in
the compared string, or all compared
characters match but the compared
string is longer.
String Comparison

String – BuiltIn Functions
string str;
str="DSA lecture";
int l=str.length();
cout<<l;
string str;
str="DSA lecture";
int l=str.length();
cout<<l<<endl;
int pat= str.find('A');
cout<<pat;

Q1. What is the difference between function member
that are virtual and those that are not?
Q2. Write an algorithm or Pseudo code that Counts al
zeros, Odd numbers and even number in a linear array
Q3. Consider 2D.Linear arrays AAA[4][5].
(a) Find the total number of elements.
(b) Suppose Base(AAA) = 300 and w=4 words per
memory cell for AAA. Find the address of AAA[3][2] .

DSA-Lecture03-Pointers, Strings(outputs).pptx

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