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"Just loop and grow the sequence.
JavaScript specific.
/**
* @param {number} n
* @return {string}
*/
var countAndSay = function(n) {
let num = '1'
while (--n > 0) {
num = num.match(/(\d)\1*/g).map(x => x.length + x[0]).join('')
}
return num
};General solution.
/**
* @param {number} n
* @return {string}
*/
var countAndSay = function(n) {
let num = '1'
while (--n > 0) {
let newNum = ''
for (let i = 0, accu = 1; i < num.length; i++, accu++) {
if (num[i] !== num[i+1]) {
newNum += accu + num[i]
accu = 0
}
}
num = newNum
}
return num
};