C++ Operators

1. Arithmetic Operators

Perform mathematical operations.

Increment/Decrement:

cpp

int x = 5;
int y = ++x;  // Pre-increment: x=6, y=6
int z = x++;  // Post-increment: z=6, x=7

int a = 10;
int b = --a;  // Pre-decrement: a=9, b=9
int c = a--;  // Post-decrement: c=9, a=8

2. Relational Operators

Compare values, return bool (true/false).

cpp

int a = 10, b = 20;
cout << (a == b) << endl;  // 0 (false)
cout << (a != b) << endl;  // 1 (true)
cout << (a < b) << endl;   // 1 (true)
cout << (a >= 10) << endl; // 1 (true)

3. Logical Operators

Combine boolean expressions.

cpp

int age = 25;
bool hasLicense = true;

// AND operator
if(age >= 18 && hasLicense) {
    cout << "Can drive" << endl;
}

// OR operator
if(age < 13 || age > 65) {
    cout << "Eligible for discount" << endl;
}

// NOT operator
bool isWeekend = false;
if(!isWeekend) {
    cout << "It's a weekday" << endl;
}

// Short-circuit evaluation
int x = 0;
if(x != 0 && 10/x > 2) {  // Second part not evaluated if first is false
    // Safe from division by zero
}

4. Bitwise Operators

Operate on individual bits.

cpp

unsigned int a = 5;  // 0101 in binary
unsigned int b = 3;  // 0011 in binary

cout << "a & b = " << (a & b) << endl;   // 0001 = 1
cout << "a | b = " << (a | b) << endl;   // 0111 = 7
cout << "a ^ b = " << (a ^ b) << endl;   // 0110 = 6
cout << "~a = " << (~a) << endl;         // 1111 1010 = 250 (unsigned)
cout << "a << 1 = " << (a << 1) << endl; // 1010 = 10
cout << "a >> 1 = " << (a >> 1) << endl; // 0010 = 2

// Practical uses:
// Check if number is even/odd
if(x & 1) {
    cout << x << " is odd" << endl;  // Last bit is 1
} else {
    cout << x << " is even" << endl; // Last bit is 0
}

// Multiply/divide by powers of 2
int num = 10;
int doubled = num << 1;  // 20 (10*2)
int halved = num >> 1;   // 5 (10/2)

// Set bit at position
int setBit(int num, int pos) {
    return num | (1 << pos);
}

// Clear bit at position
int clearBit(int num, int pos) {
    return num & ~(1 << pos);
}

5. Assignment Operators

Assign values to variables.

cpp

int x = 10;
x += 5;   // x = 15
x -= 3;   // x = 12
x *= 2;   // x = 24
x /= 4;   // x = 6
x %= 4;   // x = 2

// Chaining assignment
int a, b, c;
a = b = c = 10;  // All set to 10

// Compound assignment with expressions
int y = 5;
y += 3 * 2;  // y = y + (3*2) = 11

6. Operator Precedence

Order in which operators are evaluated.

Examples:

cpp

int result = 5 + 3 * 2;      // 11 (multiplication first)
int result2 = (5 + 3) * 2;   // 16 (parentheses change order)

bool logical = 5 > 3 && 10 < 20;  // true (&& after comparisons)

int a = 5, b = 3, c = 2;
int expr = a + b * c;        // 11 (b*c = 6, +5)
int expr2 = (a + b) * c;     // 16

// Tricky precedence
int x = 5, y = 10, z = 15;
bool test = x + 5 > y && y < z;  // (x+5)>y && (y<z) = true

// Use parentheses for clarity
int unclear = a & b == 2;     // Wrong: b==2 evaluated first
int clear = (a & b) == 2;     // Correct

Conditional Statements

1. if Statement

cpp

if(condition) {
    // code executes if condition is true
}

Simple Example:

cpp

int age = 20;
if(age >= 18) {
    cout << "You are an adult" << endl;
}

2. if-else Statement

cpp

if(condition) {
    // code if condition is true
} else {
    // code if condition is false
}

Example:

cpp

int score = 75;
if(score >= 50) {
    cout << "Pass" << endl;
} else {
    cout << "Fail" << endl;
}

3. else-if Ladder

cpp

if(condition1) {
    // code if condition1 is true
} else if(condition2) {
    // code if condition2 is true
} else if(condition3) {
    // code if condition3 is true
} else {
    // code if all conditions are false
}

Example:

cpp

int marks = 85;
char grade;

if(marks >= 90) {
    grade = 'A';
} else if(marks >= 80) {
    grade = 'B';
} else if(marks >= 70) {
    grade = 'C';
} else if(marks >= 60) {
    grade = 'D';
} else {
    grade = 'F';
}
cout << "Grade: " << grade << endl;

4. Nested Conditions

cpp

if(condition1) {
    if(condition2) {
        // code if both conditions are true
    }
}

Example:

cpp

int age = 25;
bool hasLicense = true;

if(age >= 18) {
    if(hasLicense) {
        cout << "Can drive a car" << endl;
    } else {
        cout << "Need to get a license first" << endl;
    }
} else {
    cout << "Too young to drive" << endl;
}

// Alternative with logical operators
if(age >= 18 && hasLicense) {
    cout << "Can drive a car" << endl;
}

5. switch Statement

Used for multiple choices based on a single value.

cpp

switch(expression) {
    case constant1:
        // code
        break;
    case constant2:
        // code
        break;
    default:
        // code if no case matches
}

Example:

cpp

int day = 3;
switch(day) {
    case 1:
        cout << "Monday" << endl;
        break;
    case 2:
        cout << "Tuesday" << endl;
        break;
    case 3:
        cout << "Wednesday" << endl;
        break;
    case 4:
        cout << "Thursday" << endl;
        break;
    case 5:
        cout << "Friday" << endl;
        break;
    case 6:
        cout << "Saturday" << endl;
        break;
    case 7:
        cout << "Sunday" << endl;
        break;
    default:
        cout << "Invalid day" << endl;
}

Important Notes:

• Expression must be integral or enum type

• break is needed to exit switch

• Cases can be combined

• default is optional

Combined Cases:

cpp

char grade = 'B';
switch(grade) {
    case 'A':
    case 'B':
    case 'C':
        cout << "Pass" << endl;
        break;
    case 'D':
    case 'F':
        cout << "Fail" << endl;
        break;
    default:
        cout << "Invalid grade" << endl;
}

switch vs if-else:

cpp

// Equivalent if-else for switch example
if(day == 1) {
    cout << "Monday" << endl;
} else if(day == 2) {
    cout << "Tuesday" << endl;
} // ... and so on

Modern C++17 if with initializer:

cpp

if(int result = calculate(); result > 100) {
    cout << "Large result: " << result << endl;
}
// result is out of scope here

Conditional Operator (Ternary):

cpp

// Syntax: condition ? expression1 : expression2
int a = 10, b = 20;
int max = (a > b) ? a : b;  // Returns larger value

// Equivalent to:
if(a > b) {
    max = a;
} else {
    max = b;
}

// Can be nested (avoid for clarity)
int score = 75;
string result = (score >= 50) ? 
                ((score >= 80) ? "Distinction" : "Pass") : 
                "Fail";

Loops

1. for Loop

cpp

for(initialization; condition; update) {
    // code to repeat
}

Examples:

cpp

// Basic for loop
for(int i = 0; i < 5; i++) {
    cout << i << " ";  // Output: 0 1 2 3 4
}

// Multiple variables
for(int i = 0, j = 10; i < j; i++, j--) {
    cout << i << "-" << j << " ";  // 0-10 1-9 2-8 3-7 4-6
}

// Reverse loop
for(int i = 10; i > 0; i--) {
    cout << i << " ";
}

// Infinite loop (avoid!)
// for(;;) {
//     // infinite loop
// }

// Range-based for loop (C++11)
vector<int> numbers = {1, 2, 3, 4, 5};
for(int num : numbers) {
    cout << num << " ";
}

// With auto
for(auto num : numbers) {
    cout << num << " ";
}

// Reference to modify
for(int& num : numbers) {
    num *= 2;  // Double each element
}

2. while Loop

cpp

while(condition) {
    // code to repeat while condition is true
}

Examples:

cpp

// Basic while loop
int i = 0;
while(i < 5) {
    cout << i << " ";
    i++;
}

// User input validation
int number;
cout << "Enter positive number: ";
cin >> number;
while(number <= 0) {
    cout << "Invalid! Enter positive number: ";
    cin >> number;
}

// Infinite loop with break
while(true) {
    // do something
    if(exitCondition) {
        break;
    }
}

3. do-while Loop

cpp

do {
    // code executes at least once
} while(condition);

Examples:

cpp

// Basic do-while
int i = 0;
do {
    cout << i << " ";
    i++;
} while(i < 5);

// Menu system
int choice;
do {
    cout << "\n1. Add\n2. Subtract\n3. Exit\nChoice: ";
    cin >> choice;
    
    switch(choice) {
        case 1: /* add */ break;
        case 2: /* subtract */ break;
        case 3: cout << "Exiting..." << endl; break;
        default: cout << "Invalid choice" << endl;
    }
} while(choice != 3);

// Guaranteed execution at least once
char answer;
do {
    cout << "Do you want to continue? (y/n): ";
    cin >> answer;
} while(answer != 'y' && answer != 'n');

while vs do-while:

cpp

int x = 10;

// while - condition checked first
while(x < 5) {
    cout << "This won't execute";
}

// do-while - executes once before checking
do {
    cout << "This executes once";  // Executes even though x=10
} while(x < 5);

4. Nested Loops

Loop inside another loop.

cpp

for(int i = 0; i < 3; i++) {
    for(int j = 0; j < 3; j++) {
        cout << "(" << i << "," << j << ") ";
    }
    cout << endl;
}
// Output:
// (0,0) (0,1) (0,2)
// (1,0) (1,1) (1,2)
// (2,0) (2,1) (2,2)

Examples:

cpp

// Multiplication table
for(int i = 1; i <= 10; i++) {
    for(int j = 1; j <= 10; j++) {
        cout << i * j << "\t";
    }
    cout << endl;
}

// Pattern printing
int rows = 5;
for(int i = 1; i <= rows; i++) {
    for(int j = 1; j <= i; j++) {
        cout << "* ";
    }
    cout << endl;
}
// Output:
// *
// * *
// * * *
// * * * *
// * * * * *

// 2D array traversal
int matrix[3][3] = {{1,2,3},{4,5,6},{7,8,9}};
for(int i = 0; i < 3; i++) {
    for(int j = 0; j < 3; j++) {
        cout << matrix[i][j] << " ";
    }
    cout << endl;
}

5. break & continue

break Statement:

Exits the current loop immediately.

cpp

// Search for number
int numbers[] = {1, 3, 5, 7, 9, 2, 4, 6, 8};
int target = 7;

for(int i = 0; i < 9; i++) {
    if(numbers[i] == target) {
        cout << "Found at position " << i << endl;
        break;  // Exit loop early
    }
}

// In switch
int day = 2;
switch(day) {
    case 1: cout << "Mon"; break;
    case 2: cout << "Tue"; break;  // Exit switch
}

// Breaking nested loops
for(int i = 0; i < 3; i++) {
    for(int j = 0; j < 3; j++) {
        if(i * j == 4) {
            cout << "Found at " << i << "," << j << endl;
            break;  // Only breaks inner loop
        }
    }
}

continue Statement:

Skips to the next iteration of the loop.

cpp

// Print odd numbers only
for(int i = 1; i <= 10; i++) {
    if(i % 2 == 0) {
        continue;  // Skip even numbers
    }
    cout << i << " ";  // Output: 1 3 5 7 9
}

// Skip invalid input
for(int i = 0; i < 5; i++) {
    int num;
    cout << "Enter positive number: ";
    cin >> num;
    
    if(num <= 0) {
        cout << "Invalid, skipping..." << endl;
        continue;  // Skip this iteration
    }
    
    cout << "Processing " << num << endl;
}

// In while loop
int i = 0;
while(i < 10) {
    i++;
    if(i % 3 == 0) {
        continue;  // Skip multiples of 3
    }
    cout << i << " ";
}
// Output: 1 2 4 5 7 8 10

Loop Control Examples:

Prime Number Check:

cpp

int num = 17;
bool isPrime = true;

if(num <= 1) {
    isPrime = false;
} else {
    for(int i = 2; i <= num/2; i++) {
        if(num % i == 0) {
            isPrime = false;
            break;  // No need to check further
        }
    }
}

cout << num << " is " << (isPrime ? "prime" : "not prime") << endl;

Fibonacci Series:

cpp

int n = 10;
int a = 0, b = 1;

cout << "Fibonacci: " << a << " " << b << " ";
for(int i = 2; i < n; i++) {
    int next = a + b;
    cout << next << " ";
    a = b;
    b = next;
}

Menu System with Loop:

cpp

#include <iostream>
using namespace std;

int main() {
    int choice;
    
    do {
        cout << "\n=== Calculator ===" << endl;
        cout << "1. Add" << endl;
        cout << "2. Subtract" << endl;
        cout << "3. Multiply" << endl;
        cout << "4. Divide" << endl;
        cout << "5. Exit" << endl;
        cout << "Enter choice: ";
        cin >> choice;
        
        if(choice >= 1 && choice <= 4) {
            double num1, num2;
            cout << "Enter two numbers: ";
            cin >> num1 >> num2;
            
            switch(choice) {
                case 1:
                    cout << "Result: " << num1 + num2 << endl;
                    break;
                case 2:
                    cout << "Result: " << num1 - num2 << endl;
                    break;
                case 3:
                    cout << "Result: " << num1 * num2 << endl;
                    break;
                case 4:
                    if(num2 != 0) {
                        cout << "Result: " << num1 / num2 << endl;
                    } else {
                        cout << "Error: Division by zero!" << endl;
                    }
                    break;
            }
        } else if(choice != 5) {
            cout << "Invalid choice!" << endl;
        }
        
    } while(choice != 5);
    
    cout << "Goodbye!" << endl;
    return 0;
}

Modern Loop Features:

Structured Bindings (C++17):

cpp

#include <map>
#include <iostream>

int main() {
    std::map<std::string, int> scores = {{"Alice", 95}, {"Bob", 87}, {"Charlie", 92}};
    
    for(const auto& [name, score] : scores) {
        std::cout << name << ": " << score << std::endl;
    }
    
    return 0;
}

Initializer in if/switch (C++17):

cpp

if(auto it = myMap.find(key); it != myMap.end()) {
    // Use it here
} // it is destroyed here

switch(int value = getValue(); value) {
    case 1: /* ... */ break;
    case 2: /* ... */ break;
}

Common Patterns:

Reading until sentinel:

cpp

int value;
while(cin >> value && value != -1) {
    // Process value
}

Input validation:

cpp

int age;
do {
    cout << "Enter age (0-120): ";
    cin >> age;
} while(age < 0 || age > 120);

Pattern printing:

cpp

// Pyramid pattern
int rows = 5;
for(int i = 1; i <= rows; i++) {
    // Print spaces
    for(int j = 1; j <= rows - i; j++) {
        cout << " ";
    }
    // Print stars
    for(int k = 1; k <= (2*i - 1); k++) {
        cout << "*";
    }
    cout << endl;
}

This extensive guide covers all essential operators and control flow constructs in C++. Practice these concepts with coding exercises to build strong fundamentals!