Create 038. Count and Say

Author: haibarawu

038. Count and Say

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+/*
+ * @lc app=leetcode id=38 lang=java
+ *
+ * [38] Count and Say
+ *
+ * https://leetcode.com/problems/count-and-say/description/
+ *
+ * algorithms
+ * Easy (38.98%)
+ * Total Accepted:    249.1K
+ * Total Submissions: 637.9K
+ * Testcase Example:  '1'
+ *
+ * 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"
+ * 
+ */
+class Solution {
+    public String countAndSay(int n) {
+        if(n <= 0) {
+            return "";
+        }
+        
+        String result = "1";
+        int start = 1;
+        
+        while(start < n) {
+            StringBuilder str = new StringBuilder();
+            int count = 1;
+            
+            for(int i = 1; i < result.length(); i++) {
+                if(result.charAt(i) == result.charAt(i-1)) {
+                    count++;
+                }  
+                else {
+                    str.append(count);
+                    str.append(result.charAt(i-1));
+                    count = 1;
+                }
+            }
+            
+            str.append(count);
+            str.append(result.charAt(result.length()-1));
+            result = str.toString();
+            start++;
+        }
+
+        return result;
+    }
+}