Given two strings, determine the edit distance between them. The edit distance is defined as the minimum number of edits (insertion, deletion, or substitution) needed to change one string to the other.

getEditDistance.ts

const getEditDistance = function(a: string, b: string):number{

  if(!a.length) return b.length; 
  if(!b.length) return a.length; 

  const matrix:number[][] = [];
  
  // fill first row and column 
  for(let i = 0; i <= b.length; i++){
    matrix[i] = [i];
  }
  for(let j = 0; j <= a.length; j++){
    matrix[0][j] = j;
  }

  // fill the rest of the matrix
  for(let i = 1; i <= b.length; i++){
    for(let j = 1; j <= a.length; j++){

      // different char, calculate min
      if(b[i-1] != a[j-1]){
         matrix[i][j] = Math.min(matrix[i-1][j-1] + 1,matrix[i][j-1] + 1, matrix[i-1][j] + 1); 
      // same char, no operation, use previous min value
      } else {
          matrix[i][j] = matrix[i-1][j-1];
      }
    }
  }

  return matrix[b.length][a.length];
};