Let's Do Algorithms - Part One

In this series, I will be sharing some algorithm problems and my solutions to the algorithm. The solutions are written in C#.

We all know the importance of the algorithm in computer programming. Solving algorithms helps us to hone our coding and program solving skills. I am currently practicing various algorithms and had a thought to share with the community so that I can get suggestions, better solutions on it and also it will help others.

 

In this series, I will be sharing some algorithm problems and my solutions to the algorithm. The solutions are written in C#.

 

Problem 1- Reverse a String

 

Difficulty level- Easy  

 

Test Cases:

 

Input- Test                       Output- tseT

 
Solution

private static string ReverseAString(string sInput) {
 string sReverseString = string.Empty;
 int iStringLength = sInput.Length - 1;
 while (iStringLength >= 0) {
  sReverseString += sInput[iStringLength];
  iStringLength--;
 }

 return sReverseString;
}

Note

For Reverse string using a stack, you can refer to my blog.

 

Problem 2- Reverse an integer 

 

Given a 32-bit signed integer, reverse digits of an integer.

 

Note
The function should return 0 when the reversed integer overflows.

 

Difficulty level- Easy 

Test Cases-

Input- 1234                             Output-4321

Input-1534236469                  Output-0

 

Solution

public class Solution {
    public int Reverse(int x) {
        long lReverse = 0;
            while (x != 0)
            {
              lReverse = (lReverse * 10) + x % 10;
                x = x / 10;
            }
            return lReverse==(int)lReverse?(int)lReverse:0;
    }
}

Problem 3

 

Product of an Array. Given an integer array nums where n > 1, return an output array such that output[i] is equal to the product of all the elements of nums except nums[i].

 

Difficulty level- Medium

 

Test Cases

 

Input- [1, 2, 3, 4, 5]         Output- [24,12,8,6]

Input- [3, 2, 1]                 Output- [2, 3, 6].

 

Solution

public class Solution {
    public int[] ProductExceptSelf(int[] nums) {
        int n = nums.Length;

        int[] leftArr = new int[n];
        int[] rightArr = new int[n];

        int[] prodArr = new int[n];

        leftArr[0] = 1;
        rightArr[n - 1] = 1;

        for (int i = 1; i < n; i++)
        {
            leftArr[i] = nums[i - 1] * leftArr[i - 1];
        }


        for (int i = n - 2; i >= 0; i--)
        {
            rightArr[i] = nums[i + 1] * rightArr[i + 1];
        }


        for (int i = 0; i < n; i++)
        {
            prodArr[i] = leftArr[i] * rightArr[i];

        }

      return prodArr;
    }
}

Problem 4     

 

Given a list of numbers and a number Sum, return whether any two numbers from the list add up to Sum.

 

Difficulty level- Easy 

 

Test Case- Given [12, 15, 9, 8] and Sum of 20, return true since 12 + 8 is 20.

 

Solution

class Program
   {
       static void Main(string[] args)
       {
           List<int> lst= new List<int>(){12, 15, 9, 8};
           int sum = 20;

           Console.WriteLine(ValidateResult(lst, sum) ? "True" : "False");
           Console.Read();
       }

       private static bool ValidateResult(List<int> lst, int sum)
       {
           return lst.Any(t => lst.Contains(sum - t));
       }
   }

Hope you enjoyed the content of this blog. Stay Tuned!!!!