topic description
字符串压缩。利用字符重复出现的次数，编写一种方法，实现基本的字符串压缩功能。比如，字符串aabcccccaaa会变为a2b1c5a3。若“压缩”后的字符串没有变短，则返回原先的字符串。你可以假设字符串中只包含大小写英文字母（a至z）。
示例1:
输入："aabcccccaaa"
输出："a2b1c5a3"
示例2:
输入："abbccd"
输出："abbccd"
解释："abbccd"压缩后为"a1b2c2d1"，比原字符串长度更长。
提示：
字符串长度在[0, 50000]范围内。
来源：力扣（LeetCode）
链接：https://leetcode.cn/problems/compress-string-lcci
著作权归领扣网络所有。商业转载请联系官方授权，非商业转载请注明出处。Start solving problems (python to swift)
Check step by step
Example 1 (input: "abbc", output: "abbc")
Example 2 (input: "abcc", output: "abcc")
practical application
This function can be used in the following scenarios:
- Data compression: When a large amount of text data needs to be stored or transmitted, using this function can effectively reduce the size of the data and save storage and transmission costs.
- Data analysis: When you need to analyze string data, you can use this function to compress the data, reducing analysis time and computing resource consumption.
- Data transmission: When string data needs to be transmitted through the network, using this function can reduce the data transmission time and network bandwidth usage.
- Data display: When it is necessary to display string data on the interface, using this function can reduce the display space and improve user experience.
- Data storage: When string data needs to be stored in a database or a file, using this function can reduce storage space occupation and improve storage efficiency.
It should be noted that this compression function is only applicable to the same characters that appear consecutively. If there are identical characters that do not appear consecutively in the string, it cannot be compressed correctly. In addition, for shorter strings, the compressed string may be longer than the original string, so it is necessary to determine whether the compressed length is shorter than the original string before use.