Deletion distance - first time I wrote dynamic programming for the algorithm - I spent 25 minutes and completed the task.

DeletionDistance_dynamicProgramming_30minuteMock.cs

using System;

class Solution
{
    public static int DeletionDistance(string str1, string str2) // heat, hit
    {
      if(str1 == null && str2 == null) // false 
      {
         return 0;  
      }
      
      if(str1 == null)  // false 
      {
        return str2.Length;
      }
      
      if(str2 == null) // false 
      {
        return str1.Length; 
      }
      
      var length1 = str1.Length; // 4
      var length2 = str2.Length; // 3
      
      var deletionDistance = new int[length1 + 1, length2 + 1]; 
      
      for(int col = 0; col < length2 + 1; col++) // base case 
      {
        deletionDistance[0, col] = col; 
      }
      
      for(int row = 0; row < length1 + 1; row++)
      {
        deletionDistance[row, 0] = row; 
      }
      
      for(int row = 1; row < length1 + 1; row++)
      {
        for(int col = 1; col < length2 + 1; col++)
        {
          // it is equal 
          var firstChar  = str1[row - 1]; // heat -> left -> right 
          var secondChar = str2[col - 1];  //hit
          
          var isSame = firstChar == secondChar; 
          if(isSame)
          {
            deletionDistance[row, col] = deletionDistance[row - 1, col - 1]; 
          }
          else 
          {          
            deletionDistance[row, col] = 1 + Math.Min(deletionDistance[row - 1, col], deletionDistance[row, col - 1]); 
          }
        }
      }
      
      return deletionDistance[length1, length2]; 
    }

    static void Main(string[] args)
    {
        Console.WriteLine(DeletionDistance("heat","hit")); 
    }
}

/*

---------------------
|
|
|    ^
|  < 

heat  = length1   
hit   = length2 

     0  1  2   3     4      total length = length1 + 1, 0 - length1
    ""  t  at  eat   heat   
0
1              u
2          l   ?
3
..
.
length2 + 1

base case: 
one thing is empty, distance

both distance 0 

subproblem

say that dynamic programming today 

h -> 0
eat -> 1 + Math.Min(dist("at", "it"), dist("eat", "t"))
it  -> 

ht 

dog
frog

d, f
og-> frog
f, r -> 3 

some some
0

some thing

4 + 5 = 9
"" "" 0
*/