《程序员面试金典（第 6 版）》 01.06. 字符串压缩

[Tcdian]

《程序员面试金典（第 6 版）》 01.06. 字符串压缩

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）。

Example 1

Input: "aabcccccaaa"
Output: "a2b1c5a3"

Example 2

Input: "abbccd"
Output: "abbccd"
Explanation: 
The compressed string is "a1b2c2d1", which is longer than the original string.

Note

• 0 <= S.length <= 50000

[Tcdian]

Solution

• JavaScript Solution

/**
 * @param {string} S
 * @return {string}
 */
var compressString = function(S) {
    if (S.length <= 2) {
        return S;
    }
   let base = 0;
   let result = '';
   for (let i = 1; i <= S.length; i++) {
       if (i === S.length || S[base] !== S[i]) {
           result += S[base] + (i - base);
           base = i;
       }
   }
   return S.length > result.length ? result : S;
};