Top 100 C++ Coding Interview Questions and Answers (2024) (2024)

// C++ Program to check whether a number is positive or// negative#include <iostream>using namespace std;int main(){ int number; number = -100; if (number >= 0) { cout << number << " is a positive number." << endl; } else { cout << number << " is a negative number." << endl; } return 0;}

// C++ program to find greatest// among three numbers using#include <iostream>using namespace std;int main(){ int a = 10, b = 20, c = 30; cout << "The Greatest Among Three Numbers is : "; if (a >= b && a >= c) { cout << a << endl; } else if (b >= a && b >= c) { cout << b << endl; } else { cout << c << endl; } return 0;}

// C++ program to check// for even or odd#include <iostream>using namespace std;// Returns true if n is// even, else oddbool isEven(int n) { return (n % 2 == 0); }// Driver codeint main(){ int n = 247; if (isEven(n) == true) { cout << "Even" << endl; } else { cout << "Odd"; } return 0;}

// C++ Program to find ASCII value of a character#include <iostream>using namespace std;int main(){ char ch; ch = 'A'; cout << "The ASCII value of " << ch << " is " << int(ch) << endl; return 0;}

// C++ Program to print whether a character is vowel or not#include <cctype>#include <iostream>using namespace std;int main(){ char ch = 'e'; if (isalpha(ch)) { if (ch == 'a' || ch == 'e' || ch == 'i' || ch == 'o' || ch == 'u' || ch == 'A' || ch == 'E' || ch == 'I' || ch == 'O' || ch == 'U') { cout << ch << " is a vowel." << endl; } else { cout << ch << " is a consonant." << endl; } } else { cout << ch << " is not an alphabet." << endl; } return 0;}

// C++ program to print whether a character is an alphabet// or not#include <cctype>#include <iostream>using namespace std;int main(){ char ch; ch = 'a'; if (isalpha(ch)) { cout << ch << " is an alphabet." << endl; } else { cout << ch << " is not an alphabet." << endl; } return 0;}

// C++ Program to find the length of a string without using// strlen()#include <cstring>#include <iostream>using namespace std;int main(){ string str = "GeeksforGeeks"; int length = 0; for (int i = 0; str[i] != '\0'; i++) { length++; } cout << "The length of the string is: " << length << endl; return 0;}

// C++ Program to toggle string#include <cstring>#include <iostream>using namespace std;int main(){ string str = "GeeksforGeeks"; for (int i = 0; str[i] != '\0'; i++) { if (islower(str[i])) { str[i] = toupper(str[i]); } else if (isupper(str[i])) { str[i] = tolower(str[i]); } } cout << "Toggled string: " << str << endl; return 0;}

// C++ Program to count the number of vowels#include <cstring>#include <iostream>using namespace std;int main(){ string str = "GeeksforGeeks to the moon"; int vowels = 0; for (int i = 0; str[i] != '\0'; i++) { if (str[i] == 'a' || str[i] == 'e' || str[i] == 'i' || str[i] == 'o' || str[i] == 'u' || str[i] == 'A' || str[i] == 'E' || str[i] == 'I' || str[i] == 'O' || str[i] == 'U') { vowels++; } } cout << "Number of vowels in the string: " << vowels << endl; return 0;}

// C++ Program to remove the vowels from a string#include <cstring>#include <iostream>using namespace std;int main(){ int j = 0; string str = "GeeksforGeeks"; for (int i = 0; str[i] != '\0'; i++) { if (str[i] != 'a' && str[i] != 'e' && str[i] != 'i' && str[i] != 'o' && str[i] != 'u' && str[i] != 'A' && str[i] != 'E' && str[i] != 'I' && str[i] != 'O' && str[i] != 'U') { str[j++] = str[i]; } } while (j < str.size()) { str[j] = '\0'; j++; } cout << "String without vowels: " << str << endl; return 0;}

// C++ Programto remove all characters from a string except// alphabets#include <cctype>#include <iostream>#include <string>using namespace std;string remove_non_alphabets(string str){ string result = ""; for (char c : str) { if (isalpha(c)) { result += c; } } return result;}int main(){ string str = "Gee$ksfor$geeks"; cout << "Alphabets only: " << remove_non_alphabets(str) << endl; return 0;}

// C++ Program to remove spaces from a string#include <iostream>#include <string>using namespace std;string remove_spaces(string str){ string result = ""; for (char c : str) { if (c != ' ') { result += c; } } return result;}int main(){ string str = "Gfg to the moon"; cout << "Without spaces: " << remove_spaces(str) << endl; return 0;}

// C++ program to find// Sum of first// n natural numbers.#include <iostream>using namespace std;// Function to find sumint findSum(int n){ int sum = 0; for (int i = 1; i <= n; i++) sum = sum + i; return sum;}int main(){ int n = 7; cout << findSum(n); return 0;}

// C++ program to find factorial using loops#include <bits/stdc++.h>using namespace std;// function to find factorialint factorial(int n){ int fact = 1; while (n > 1) { fact *= n; n--; } return fact;}// driver codeint main(){ int num = 5; cout << factorial(num); return 0;}

// C++ program to check if a given// year is leap year or not#include <iostream>using namespace std;bool checkYear(int year){ // leap year if (year % 400 == 0) return true; // Not leap year if (year % 100 == 0) return false; // leap year if (year % 4 == 0) return true; // Not leap year return false;}int main(){ int year = 2000; if (checkYear(year)) cout << "Leap Year"; else cout << "Not a Leap Year"; return 0;}

// C++ program to check if a// Number is prime#include <iostream>using namespace std;bool isPrime(int n){ // base condition if (n <= 1) return false; // Check from 2 to n-1 for (int i = 2; i < n; i++) if (n % i == 0) return false; return true;}int main(){ isPrime(21) ? cout << " true\n" : cout << " false\n"; isPrime(17) ? cout << " true\n" : cout << " false\n"; return 0;}

// C++ program to check if a// number is Palindrome or not#include <iostream>using namespace std;// Function to check Palindromebool checkPalindrome(int n){ int ans = 0; int temp = n; while (temp != 0) { ans = (ans * 10) + (temp % 10); temp = temp / 10; } return (ans == n);}int main(){ int n = 12321; if (checkPalindrome(n) == 1) { cout << "Yes\n"; } else { cout << "No\n"; } return 0;}

// C++ Program to check// if number is Armstrong// or not#include <iostream>using namespace std;int main(){ int n = 153; int temp = n; int ans = 0; // function to calculate // the sum of individual digits while (n > 0) { int rem = n % 10; ans = (ans) + (rem * rem * rem); n = n / 10; } // condition to check if (temp == ans) { cout << ("Yes, it is Armstrong Number"); } else { cout << ("No, it is not an Armstrong Number"); } return 0;}

// C++ Program to Find the// Nth Term of the Fibonacci Series#include <iostream>using namespace std;int fib(int n){ int first = 0, second = 1, ans; if (n == 0) return first; for (int i = 2; i <= n; i++) { ans = first + second; first = second; second = ans; } return ans;}int main(){ int n = 13; cout << fib(n); return 0;}

// C++ program to find// GCD of two numbers#include <iostream>using namespace std;// Function to return gcd of a and bint gcd(int a, int b){ int result = min(a, b); while (result > 0) { if (a % result == 0 && b % result == 0) { break; } result--; } return result;}int main(){ int a = 54, b = 33; cout << "GCD: " << gcd(a, b); return 0;}

// C++ program to// Find LCM of two numbers#include <iostream>using namespace std;long long gcd(long long int a, long long int b){ if (b == 0) return a; return gcd(b, a % b);}// Function to return LCM of two numberslong long lcm(int a, int b){ long long result = (a / gcd(a, b)) * b; return result;}int main(){ int a = 24, b = 13; cout << "LCM : " << lcm(a, b); return 0;}

// C++ program to find// Roots of a quadratic equation#include <iostream>#include <math.h>using namespace std;// Prints roots of quadratic equation ax*2 + bx + cvoid findRoots(int a, int b, int c){ // If a is 0, then equation is not quadratic if (a == 0) { cout << "Invalid"; return; } // Formulae to calculate D int d = b * b - 4 * a * c; // Formulae to calculate // square root of D double sqrt_val = sqrt(abs(d)); // Conditons for checking root if (d > 0) { cout << "Roots are real and different \n"; cout << (double)(-b + sqrt_val) / (2 * a) << "\n" << (double)(-b - sqrt_val) / (2 * a); } else if (d == 0) { cout << "Roots are real and same \n"; cout << -(double)b / (2 * a); } else { cout << "Roots are complex \n"; cout << -(double)b / (2 * a) << " + i" << sqrt_val / (2 * a) << "\n" << -(double)b / (2 * a) << " - i" << sqrt_val / (2 * a); }}int main(){ int a = 1, b = 4, c = 4; findRoots(a, b, c); return 0;}

// C++ code to for// Finding the minimum// And maximum of the array#include <iostream>using namespace std;// Function to find the minimum// and maximum of the arrayvoid findMinMax(int arr[], int n){ int mini = arr[0]; int maxi = arr[0]; for (int i = 0; i < n; i++) { if (arr[i] < mini) { mini = arr[i]; } else if (arr[i] > maxi) { maxi = arr[i]; } } cout << "Min: " << mini << endl; cout << "Max: " << maxi << endl;}int main(){ int arr[] = { 1, 2, 3, 4, 5 }; int N = sizeof(arr) / sizeof(arr[0]); findMinMax(arr, N); return 0;}

// C++ program to find// Second smallest elements#include <climits>#include <iostream>using namespace std;void print2Smallest(int arr[], int n){ int first, second; if (n < 2) { cout << " Invalid Input "; return; } first = second = INT_MAX; for (int i = 0; i < n; i++) { // If current element is smaller than first // Then update both first and second if (arr[i] < first) { second = first; first = arr[i]; } // If arr[i] is in between first and second // Then update second else if (arr[i] < second && arr[i] != first) second = arr[i]; } if (second == INT_MAX) cout << "There is no second smallest element\n"; else cout << " Second smallest element is " << second << endl;}int main(){ int arr[] = { 21, 3, 15, 41, 34, 10 }; int n = sizeof(arr) / sizeof(arr[0]); print2Smallest(arr, n); return 0;}

// C++ Program to calculate// sum of elements in an array#include <iostream>using namespace std;int sum(int arr[], int n){ int sum = 0; for (int i = 0; i < n; i++) sum += arr[i]; return sum;}int main(){ int arr[] = { 1, 23, 54, 12, 9 }; int n = sizeof(arr) / sizeof(arr[0]); cout << "Sum: " << sum(arr, n); return 0;}

// C++ program for checking// if it is Palindrome or not#include <iostream>using namespace std;string isPalindrome(string S){ for (int i = 0; i < S.length() / 2; i++) { if (S[i] != S[S.length() - i - 1]) { return "No"; } } return "Yes";}int main(){ string S = "GeekeeG"; cout << isPalindrome(S); return 0;}

// C++ program to check if two strings// Are anagrams of each other#include <iostream>using namespace std;#define NO_OF_CHARS 256bool areAnagram(char* str1, char* str2){ // Create 2 count arrays and initialize all values as 0 int count1[NO_OF_CHARS] = { 0 }; int count2[NO_OF_CHARS] = { 0 }; int i; // For each character in input strings, increment count // in the corresponding count array for (i = 0; str1[i] && str2[i]; i++) { count1[str1[i]]++; count2[str2[i]]++; } if (str1[i] || str2[i]) return false; // Compare count arrays for (i = 0; i < NO_OF_CHARS; i++) if (count1[i] != count2[i]) return false; return true;}int main(){ char str1[] = "Geek"; char str2[] = "for"; if (areAnagram(str1, str2)) cout << "The two strings are anagram of each other"; else cout << "The two strings are not anagram of each " "other"; return 0;}

// C++ program to print// Diamond shape#include <iostream>using namespace std;void printDiamond(int n){ int space = n - 1; for (int i = 0; i < n; i++) { for (int j = 0; j < space; j++) cout << " "; // Print i+1 stars for (int j = 0; j <= i; j++) cout << "* "; cout << endl; space--; } space = 0; // run loop (parent loop) for (int i = n; i > 0; i--) { for (int j = 0; j < space; j++) cout << " "; // Print i stars for (int j = 0; j < i; j++) cout << "* "; cout << endl; space++; }}int main(){ printDiamond(5); return 0;}

// C++ Program to// Print Pyramid pattern#include <iostream>using namespace std;void pattern(int n){ int k = 2 * n - 2; for (int i = 0; i < n; i++) { for (int j = 0; j < k; j++) cout << " "; k = k - 1; for (int j = 0; j <= i; j++) { // Printing stars cout << "* "; } cout << endl; }}int main(){ int n = 5; pattern(n); return 0;}

// C Program to print hourglass pattern#include <iostream>using namespace std;// function to print hourglass patternvoid hourglass(int rows){ // first outer loop to iterate each row for (int i = 0; i < 2 * rows - 1; i++) { // assigning comparator int comp; if (i < rows) { comp = 2 * i + 1; } else { comp = 2 * (2 * rows - i) - 3; } // first inner loop to print leading spaces for (int j = 0; j < comp; j++) { cout << ' '; } // second inner loop to print star * for (int k = 0; k < 2 * rows - comp; k++) { cout << "* "; } cout << '\n'; }}int main(){ hourglass(5); return 0;}

// C++ Program to print// star pattern given#include <iostream>using namespace std;void pattern(int n){ for (int i = 0; i <= n; i++) { for (int j = 0; j <= i; j++) { cout << "* "; } int spaces = 2 * (n - i); for (int j = 0; j < spaces; j++) { cout << " "; } for (int j = 0; j <= i; j++) { cout << "* "; } cout << endl; } // Printing bottom part. for (int i = n - 1; i >= 0; i--) { for (int j = 0; j <= i; j++) { cout << "* "; } int spaces = 2 * (n - i); for (int j = 0; j < spaces; j++) { cout << " "; } for (int j = 0; j <= i; j++) { cout << "* "; } cout << endl; }}int main(){ int n = 5; pattern(n); return 0;}

// C++ Program to print a simple pyramid#include <iostream>using namespace std;int main(){ int rows = 5; for (int i = 1; i <= rows; i++) { for (int j = rows; j >= i; j--) { cout << " "; } for (int k = 1; k <= (2 * i - 1); k++) { cout << "*"; } cout << endl; } return 0;}

// C++ Program to print inverted pyramid#include <iostream>using namespace std;int main(){ int rows = 5; for (int i = rows; i >= 1; i--) { for (int j = rows; j > i; j--) { cout << " "; } for (int k = 1; k <= (2 * i - 1); k++) { cout << "*"; } cout << endl; } return 0;}

// C++ Program to print a triangle star patter#include <iostream>using namespace std;int main(){ int rows; rows = 5; for (int i = 1; i <= rows; i++) { for (int j = 1; j <= i; j++) { cout << "*"; } cout << endl; } return 0;}

// C Program to print the Floyd's Triangle#include <stdio.h>int main(){ int rows = 4; int n = 1; // outer loop to print all rows for (int i = 0; i < rows; i++) { // innter loop to print abphabet in each row for (int j = 0; j <= i; j++) { printf("%d ", n++); } printf("\n"); } return 0;}

// C++ program to print// Pascal’s Triangle#include <iostream>using namespace std;void printPascal(int n){ int arr[n][n]; for (int line = 0; line < n; line++) { // Every line has number of integers // equal to line number for (int i = 0; i <= line; i++) { // First and last values in every row are 1 if (line == i || i == 0) arr[line][i] = 1; else arr[line][i] = arr[line - 1][i - 1] + arr[line - 1][i]; cout << arr[line][i] << " "; } cout << "\n"; }}int main(){ int n = 6; printPascal(n); return 0;}

// C++ Program to reversea string#include <cstring>#include <iostream>using namespace std;int main(){ int len; string str = "GeeksforGeeks"; len = str.size(); cout << "Reverse of the string: "; for (int i = len - 1; i >= 0; i--) { cout << str[i]; } cout << endl; return 0;}

// C++ Program to// Reverse string using// recursion#include <iostream>using namespace std;void reverse_str(string& s, int n, int i){ if (n <= i) { return; } swap(s[i], s[n]); reverse_str(s, n - 1, i + 1);}int main(){ string str = "GeeksforGeeks"; reverse_str(str, str.length() - 1, 0); cout << str << endl;}

// C++ program to check// Whether a given number// Is palindrome or not#include <bits/stdc++.h>using namespace std;bool isPalRec(char str[], int s, int n){ // If there is only one character if (s == n) return true; // If first and last // characters do not match if (str[s] != str[n]) return false; if (s < n + 1) return isPalRec(str, s + 1, n - 1); return true;}bool isPalindrome(char str[]){ int n = strlen(str); if (n == 0) return true; return isPalRec(str, 0, n - 1);}int main(){ char str[] = "GeeKeeG"; if (isPalindrome(str)) cout << "Yes"; else cout << "No"; return 0;}

// C++ Program for calculating// the length of string#include <iostream>using namespace std;int cal(char* str){ // base condition if (*str == '\0') return 0; else return 1 + cal(str + 1);}int main(){ char str[] = "GeeksforGeeks"; cout << cal(str); return 0;}

// C++ program to calculate// Factorial of given number#include <iostream>using namespace std;unsigned long long factorial(unsigned long long n){ if (n == 0 || n == 1) return 1; return n * factorial(n - 1);}int main(){ unsigned long long num = 15; cout << "Factorial of " << num << " is " << factorial(num) << endl; return 0;}

// C++ Program to count the sume of numbers in a string#include <iostream>#include <sstream>#include <string>using namespace std;int sum_of_numbers(string str){ int sum = 0; for (char ch : str) { if (isdigit(ch)) { sum += ch - '0'; } } return sum;}int main(){ string str; str = "1234"; cout << "Sum of numbers: " << sum_of_numbers(str) << endl; return 0;}

// C++ program to print all natural numbers upto// N without using semi-colon#include <iostream>using namespace std;#define N 10int main(){ static int x = 1; if (cout << x << " " && x++ < N && main()) { } return 0;}

// C++ program to check// If two numbers are equal#include <iostream>using namespace std;int main(){ int x = 3; int y = 4; cout << "X : " << x << endl; cout << "Y : " << y << endl; x = x + y; y = x - y; x = x - y; cout << endl; cout << "After:" << endl; cout << "X : " << x << endl; cout << "Y : " << y << endl; return 0;}

// C++ program to print maximum value of// unsigned int.#include <iostream>using namespace std;int main(){ unsigned int max; max = 0; max = ~max; cout << "Max value possible : " << max; return 0;}

// C++ Program to equality of// Two numbers without using// Arithmetic or comparison operator#include <iostream>using namespace std;int main(){ int a = 10, b = 10; if (a ^ b) cout << "Not-Equal"; else cout << "Equal"; return 0;}

// C++ program to find// maximum and minimum of// Two numbers without using// loop and conditions#include <iostream>using namespace std;int main(){ int a = 5, b = 10; cout << "max :" << (((a + b) + abs(a - b)) / 2) << endl; cout << "min :" << (((a + b) - abs(a - b)) / 2) << endl; return 0;}

// C++ Program to convert ocatal to decimal#include <cmath>#include <iostream>using namespace std;int main(){ int oct, dec = 0, place = 0; // 67 is an octal number with binary equivalent 110000 oct = 67; int temp = oct; while (temp) { int lastDigit = temp % 10; temp /= 10; dec += lastDigit * pow(8, place); ++place; } cout << "Decimal equivalent is: " << dec << endl; return 0;}