Coding Questions 2025 - Interview Problems with Solutions

Coding Questions - Complete Problem Set

Practice coding interview questions for IT services companies. Focus on fundamentals and clean code.

Basic Programming

1. Reverse String

C

void reverse(char str[]) {
    int n = strlen(str);
    for (int i = 0; i < n/2; i++) {
        char temp = str[i];
        str[i] = str[n-1-i];
        str[n-1-i] = temp;
    }
}

Java

public String reverse(String s) {
    char[] arr = s.toCharArray();
    int left = 0, right = arr.length - 1;
    while (left < right) {
        char temp = arr[left];
        arr[left++] = arr[right];
        arr[right--] = temp;
    }
    return new String(arr);
}

Python

def reverse_string(s):
    return s[::-1]

2. Palindrome Check

Java

public boolean isPalindrome(String s) {
    s = s.toLowerCase().replaceAll("[^a-z0-9]", "");
    int left = 0, right = s.length() - 1;
    while (left < right) {
        if (s.charAt(left++) != s.charAt(right--)) {
            return false;
        }
    }
    return true;
}

Python

def is_palindrome(s):
    s = ''.join(c.lower() for c in s if c.isalnum())
    return s == s[::-1]

3. Prime Number Check

C

int isPrime(int n) {
    if (n <= 1) return 0;
    if (n <= 3) return 1;
    if (n % 2 == 0 || n % 3 == 0) return 0;
    for (int i = 5; i * i <= n; i += 6) {
        if (n % i == 0 || n % (i + 2) == 0)
            return 0;
    }
    return 1;
}

Python

def is_prime(n):
    if n <= 1: return False
    if n <= 3: return True
    if n % 2 == 0 or n % 3 == 0: return False
    i = 5
    while i * i <= n:
        if n % i == 0 or n % (i + 2) == 0:
            return False
        i += 6
    return True

4. Fibonacci Series

Java

public void fibonacci(int n) {
    int a = 0, b = 1;
    for (int i = 0; i < n; i++) {
        System.out.print(a + " ");
        int temp = a + b;
        a = b;
        b = temp;
    }
}

Python

def fibonacci(n):
    a, b = 0, 1
    for _ in range(n):
        print(a, end=" ")
        a, b = b, a + b

5. Factorial

C

long long factorial(int n) {
    if (n == 0) return 1;
    long long res = 1;
    for (int i = 1; i <= n; i++) {
        res *= i;
    }
    return res;
}

Python

def factorial(n):
    if n == 0: return 1
    result = 1
    for i in range(1, n + 1):
        result *= i
    return result

6. Find Second Largest

Java

public int secondLargest(int[] arr) {
    int first = Integer.MIN_VALUE;
    int second = Integer.MIN_VALUE;
    for (int num : arr) {
        if (num > first) {
            second = first;
            first = num;
        } else if (num > second && num != first) {
            second = num;
        }
    }
    return second;
}

7. Two Sum

def two_sum(nums, target):
    seen = {}
    for i, num in enumerate(nums):
        if target - num in seen:
            return [seen[target - num], i]
        seen[num] = i
    return []

Related Resources

Interview Experience

Real interview experiences.

Preparation Guide

Complete preparation strategy.

---

Master fundamentals for IT services!

Last updated: January 2026