# 38. Count and Say (Easy)

https://leetcode.com/problems/count-and-say/

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 where 1 ≤ n ≤ 30, 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"```

## Solutions

``````class Solution {
public String countAndSay(int n) {
Map<Integer, String> map = new HashMap<>();
map.put(1, "1");
map.put(2, "11");
map.put(3, "21");
map.put(4, "1211");
map.put(5, "111221");

if (map.keySet().contains(n)) {
return map.get(n);
}

for (int i = 6; i <= n; i++) {
String pre = map.get(i - 1);

map.put(i, resolve(pre));
}

return map.get(n);
}

private String resolve(String s) {
String ans = "";

int count = 1;
char pre = s.charAt(0);

// 111,22,1
for (int i = 1; i < s.length(); i++) {
if (s.charAt(i) != pre) {
// ans="", count=3, pre=1
ans += count + "" + pre;

// reset count
count = 0;
}

// increase count of same char
count++;
pre = s.charAt(i);
}

ans += count + "" + pre;

return ans;
}
}
``````