30-seconds-of-code/snippets/levenshteinDistance.md

levenshteinDistance

Calculates the levenshteinDistance between two strings.

Calculates the number of changes(substitution,deletion,addition) required to convert string1 to string2. Can also be required to compare two strings as shown in example.

const levenshteinDistance  = (string1,string2) => {
    if(string1.length === 0) return string2.length;
    if(string2.length === 0) return string1.length;
    let matrix = Array(string2.length+ 1).fill(0).map((x,i) => [i]);
    matrix[0] = Array(string1.length + 1).fill(0).map((x,i) => i);
    for(i = 1;i <= string2.length;i++){
        for(j = 1;j<=string1.length; j++){
            if(string2[i-1] === string1[j-1]){
                matrix[i][j] = matrix[i-1][j-1];
            }
            else{
                matrix[i][j] = Math.min(matrix[i-1][j-1]+1,matrix[i][j-1]+1,matrix[i-1][j]+1);
            }
        }
    }
    return matrix[string2.length][string1.length]
}

levenshteinDistance('30-seconds-of-code','30-seconds-of-python-code'); // 7
const compareStrings = (string1,string2) => (100 - levenshteinDistance(string1,string2)/Math.max(string1.length,string2.length));
compareStrings('30-seconds-of-code','30-seconds-of-python-code'); // 99.72 (%)