12.外观数列

var countAndSay = function(n) {
    if (n===1) return "1";
    else {
        var str =  countAndSay(n-1);
        var temp = str[0];
        var count = 0;
        var ans = '';
        for (var i=0; i<str.length;i++){
            if (str[i]===temp) count++;
            else {
                // ans += count.toString() + temp.toString();
                ans += '' + count + temp;
                temp = str[i];
                count = 1;
            }
            // if (i===str.length-1) ans += count.toString() + temp.toString();
            if (i===str.length-1) ans += '' + count + temp;
        }
        return ans
    }
};