Leetcode-1234. 替换子串得到平衡字符串

Problem: 1234. 替换子串得到平衡字符串

思路

滑动窗口+哈希表+贪心思想

复杂度

• 时间复杂度: O(n)

• 空间复杂度: O(1)

Code

Python3

class Solution:
    def balancedString(self, s: str) -> int:
        n = len(s)
        ans = n

        cnt = Counter(s)
        
        target = n / 4

        if max(cnt.values()) <= target:
            return 0
        
        l = 0
        for r,c in enumerate(s):
            cnt[c] -= 1
            while cnt[s[l]] < target:
                cnt[s[l]] += 1
                l += 1
            if max(cnt.values()) <= target:
                ans = min(ans, r - l + 1)
        
        return ans