LeetCode 字符串的排列

Posted 2021-09-15 xhBruce

567. 字符串的排列

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• s1字符串26小写字母统计
• s2连续查找抵消s1统计
• 某个字符ch1[k] < 0时按照s2从left开始回复ch1[k]
• s2连续包含,匹配个数为s1长度i - left + 1 == n，返回true

class Solution {
    public boolean checkInclusion(String s1, String s2) {
        int n = s1.length();
        int m = s2.length();
        if (n > m) {
            return false;
        }

        int[] ch1 = new int[26];

        for (int i = 0; i < n; i++) {
            int k = s1.charAt(i) - 'a';
            ++ch1[k];
        }

        int left = 0;
        for (int i = 0; i < m; i++) {
            int k = s2.charAt(i) - 'a';
            --ch1[k];
            while (ch1[k] < 0) {
                ++ch1[s2.charAt(left) - 'a'];
                ++left;
            }
            if (i - left + 1 == n) {
                return true;
            }
        }

        return false;
    }
}