Longest Common Substring

longest_common_substring.js

/**
 * Longest Common Substring in JavaScript
 * 
 * This is the brute-force solution.
 *
 * @param {String} s1
 * @param {String} s2
 * @return {String} r1
 */

function longestCommonSubstring(s1, s2) {
    var r1 = '',
        r2 = '';

    for (var i = 0; i < s1.length; i++) {
        for (var j = 0; j < s2.length; j++) {
            if (s1[i] === s2[j]) {
                for (var k = j, c = i; k < s2.length; k++) {
                    if (s1[c] === s2[k]) {
                        r2 += s1[c];
                        c++;
                    }
                    else {
                        if (r2.length > r1.length) {
                            r1 = r2;
                        }
                        r2 = '';
                        break;
                    }
                }
            }
        }
    }

    return r1;
}