input: Write a function to compute the edit distance between two given strings. The function should return the minimum number of operations (insertions, deletions, or substitutions) required to transform one string into the other.
  assert editDistance("kitten", "sitting", len("kitten"), len("sitting"))==3
  assert editDistance("intention", "execution", len("intention"), len("execution"))==5
  assert editDistance("horse", "ros", len("horse"), len("ros"))==3
  assert editDistance("sunday", "saturday", len("sunday"), len("saturday"))==3
  assert editDistance("", "", len(""), len(""))==0
output: def editDistance(str1, str2, m, n):
      dp = [[0 for x in range(n + 1)] for x in range(m + 1)]
      
      for i in range(m + 1):
          for j in range(n + 1):
              if i == 0:
                  dp[i][j] = j
              elif j == 0:
                  dp[i][j] = i
              elif str1[i-1] == str2[j-1]:
                  dp[i][j] = dp[i-1][j-1]
              else:
                  dp[i][j] = 1 + min(dp[i][j-1], dp[i-1][j], dp[i-1][j-1])
      
      return dp[m][n]