leetcode——2020-03月：字符串的壓縮

思路

雙指針，一個輔助指針用來計數

代碼

class Solution(object):
    def compressString(self, S):
        """
        :type S: str
        :rtype: str
        """
        n = len(S)
        res = []
        i = 0
        while(i<n):
            j = i
            while(j<n and S[j] ==S[i]) :
                j +=1
            res +=S[i]
            res+=str(j-i)
            i= j
        if len(res)<len(S):
            return ''.join(res)
        else:
            return S