C++ Notes

c-string

array of chars, uses ‘0’ to end the string

char s[11]; declares c-string, creates space for 10 chars

char s[20] = “Hi There”; declares and initializ c-string char message[] - “abc”; also acceptable char message[] = {‘a’, ‘b’} not acceptable

initializing a c-string does not cause a n to be inserted

string = “hello”; not llegal assignment opperator does not work with c-string

#include<cstring> places Hello and 0 into a_string char a_string[11]; strcpy (a_string, “Hello”); strcopy does not check size of array

can write chars beyond declared size causing error

char message[10]; strncpy(message, strvar, 9); will only copy up to 9 chars

avoiding problem with str cpy *will not add ‘0’ to end

strcmp(str1, str2) if strings eqal returns 0, if str1 is less

returns negative value, if str1 is more returns positive number

strlen(str) returns number of chars in string strcat(str, “hello”) concats str with “hello”

char str[80] cin.getline(a, 80) reads entire line including spaces

cstdlib

atoi(“1234”) converts to int, if non number char - returns 0 atol converts to long atof converts to double

abs(int) labs(long)

string

standard string class

getline(cin, line) entered text assigned to string line cin.get reads one char at a time getline(cin str, ‘?’) stops at ‘?’ instead of ‘n’ cin.ignore(1000, ‘n’) reads upto 1000 chars or to ‘n’ str.length() returns length of string

comparison operators compare the lexicographic order of strings

vector

vectors (like java arrayList)

vector<int> v; creates vector of ints v[i] = 42; can change value at i but not initialize value at i

initializing a value this way will not show an error but will cause problems in the program.

v.resize(24) resizes vector to 24, elements after are lost

Pointer

pointer is memory address of a variable pointer variables must have a type

double *p; declares a pointer to a type double

& operator used to get address of variable * derefrencing operator

*p gets the variable pointed to by p

pointer notation:

int a, *b; //notation for pointer a = b; b = &a; cout << b; cout << *b; //derefrencing operator

p1 = new int; //variable can be referred to as *p1

(*head).count = 12; AND head -> count = 12; ARE THE SAME

Linked List

struct ListNode {

string item; int count; ListNode *link; //pointer to another node of type ListNode

};

typedef ListNode* ListNodePtr; (*head).count = 12; //head is pointer, *head is the node head points to

dot operator has higher precedence than the dereference operator*, so parentheses are required

head -> count = 12; //does the same as (*head).count=12;

ListNodePtr head; //head points to the first/only node head = new ListNode

Basic C++ console

#include<iostream> using namespace std; int main() {

return 0;

}

IO Basics

cout << “Hello”; output to console cin >> var1; input from consol cout << num << “is cool” output mulitple values cout << (price + tax); output arithmetic expressions << insertion operator

Formatting

cout.precision(5); number of digits after the decimal point

float output/magic formula cout.setf(ios::fixed); cout.setf(ios::showpoint); cout.precision(2);

static_cast<double>(9) converts 9 to 9.0

fstream

#include<iostream> #include<fstream> ifstream fin; fin.open(“input.txt”); fin.close() ofstream fout; fout.open(“output.txt”); fout.close()

if(fout.fail()){

cout << “error”

}

Escapes

new-line n horizonal tab t alert a backslash \ double quote ” endl same as n but should not be in quotes/strings

Namespace

a collection of names such as cin and cout each name in a namespace has one specification in the namespace

Number Types

short int long float double long double

Constants

const type_name variable_name;

Enumeration

List of constants of type int enum Month {JAN, Feb} //JAN value will be set to 0, FEB will be set to 1

Flow of Control

switch(variable){ //switch statement

case 1:

cout “do something”; break;

case 2:

cout “do somethin else”; break;

}

for(n = 1; n<=10; n++){}

//n is set to one //loop continues until statement is false //n is incremented at the end of the loop

cmath

sqrt(number) pow(num, power) fabs(double) absolute value ceil(double) round up floor(double) round down

class structure

class name {

public:

//vars + defs?

private:

//vars + defs?

}; name::method