Problem
The count-and-say sequence is the sequence of integers with the first five terms as following:
1. 1
2. 11
3. 21
4. 1211
5. 111221
1
is read off as "one 1"
or 11
.
11
is read off as "two 1s"
or 21
.
21
is read off as "one 2
, then one 1"
or 1211
.
Given an integer n, generate the nth term of the count-and-say sequence.
Note: Each term of the sequence of integers will be represented as a string.
Example 1:
Input: 1
Output: "1"
Example 2:
Input: 4
Output: "1211"
Solution
/**
* @param {number} n
* @return {string}
*/
var countAndSay = function(n) {
var str = '1';
var tmp = '';
var last = '';
var count = 0;
var len = 0;
for (var i = 1; i < n; i++) {
tmp = '';
last = '';
count = 0;
len = str.length;
for (var j = 0; j < len; j++) {
if (last === '') {
last = str[j];
count = 1;
continue;
}
if (str[j] === last) {
count += 1;
} else {
tmp += '' + count + last;
last = str[j];
count = 1;
}
}
if (last) {
tmp += '' + count + last;
}
str = tmp;
}
return str;
};
Explain:
nope.
Complexity:
- Time complexity :
- Space complexity :