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替换子串得到平衡字符串⚓︎

Leetcode题目链接

描述⚓︎

详见中文题目链接。

解答⚓︎

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class Solution {
private:
    bool check(vector<int>& cnts, int len, int require) {
        int totalAdjustments = 0;
        for (int i = 0; i < 4; i++) {
            if (cnts[i] > require) return false;
            totalAdjustments += max(0, require - cnts[i]);
        }
        return totalAdjustments <= len;
    }

public:
    int balancedString(string s) {
        int n = s.size();
        vector<int> arr(n);
        vector<int> cnts(4, 0);

        for (int i = 0; i < n; i++) {
            if (s[i] == 'Q') arr[i] = 0;
            else if (s[i] == 'W') arr[i] = 1;
            else if (s[i] == 'E') arr[i] = 2;
            else if (s[i] == 'R') arr[i] = 3;
            cnts[arr[i]]++;
        }

        int require = n / 4;
        int res = n;

        for (int left = 0, right = 0; left < n; left++) {
            while (right < n && !check(cnts, right - left, require)) {
                cnts[arr[right]]--;
                right++;
            }

            if (check(cnts, right - left, require)) {
                res = min(res, right - left);
            }

            cnts[arr[left]]++;
        }

        return res;
    }
};