1208. Get Equal Substrings Within Budget

Ref: https://leetcode-cn.com/problems/candy/

这道题思路和424类似，利用双指针可以快速实现，主要思路如下：

• 左指针不动，移动右指针计算cost，直到超过maxCount；
• 左指针移动一个单位，继续上述操作，直到right到达尾部。

代码如下：

class Solution:

    def equalSubstring(self, s: str, t: str, maxCost: int) -> int:
        l = len(s)
        s = [x for x in s]
        t = [x for x in t]
        left = 0
        right = 0
        result = 0
        max_cost = 0
        while right < l:
            max_cost += abs(ord(s[right]) - ord(t[right]))
            right += 1
            if max_cost > maxCost:
                max_cost -= abs(ord(s[left]) - ord(t[left]))
                left += 1
            result = max(result, right - left)
        return result