text-justification.js

/**
 * @param {string[]} words
 * @param {number} maxWidth
 * @return {string[]}
 */
var fullJustify = function(words, maxWidth) {
    var len = words.length;
    var arr = [];
    var width = 0;
    var item = null;
    var addLen = 0;
    var res = [];

    for (var i = 0; i < len; i++) {
        item = words[i];
        addLen = width === 0 ? item.length : (item.length + 1);

        if (width + addLen > maxWidth) {
            res.push(helper(arr, maxWidth - width, false));
            arr = [];
            width = 0;
            addLen = item.length;
        }

        arr.push(item);
        width += addLen;
    }

    res.push(helper(arr, maxWidth - width, true));

    return res;
};

var helper = function(arr, left, isLast) {
    var len = arr.length;
    var num = 0;
    var rem = 0;
    var res = '';

    if (len === 1 || isLast) {
        return arr.join(' ') + ' '.repeat(left);
    }

    num = Math.floor(left / (len - 1));
    rem = left % (len - 1);
    for (var i = 0; i < len; i++) {
        res += arr[i];
        if (i < len - 1) res += ' '.repeat(num + 1);
        if (i < rem) res += ' ';
    }

    return res;

};