[滑动窗口/哈希] leetcode 567 Permutation in String

Posted 2020-11-10 fish1996

problem:https://leetcode.com/problems/permutation-in-string/

        这道题感觉几乎和Leetcode上另一题一模一样，昨天刚刷的：https://www.cnblogs.com/fish1996/p/11269526.html,就当签到题爽一爽了。

class Solution {
public:
    bool checkInclusion(string s1, string s2) {

        vector<int> target(26, 0);
        for (int i = 0; i < s1.size(); i++)
        {
            target[s1[i] - \'a\']++;
        }

        int k = s1.size();

        vector<int> source(26, 0);
        int count = 0;
        for (int i = 0; i < s2.size(); i++)
        {
            source[s2[i] - \'a\']++;
            if (source[s2[i] - \'a\'] <= target[s2[i] - \'a\'])
            {
                count++;
            }

            if (i >= k)
            {        
                if (source[s2[i - k] - \'a\'] <= target[s2[i - k] - \'a\'])
                {
                    count--;
                }
                source[s2[i - k] - \'a\']--;
            }

            if (count == k)
            {
                return true;
            }
        }

        return false;
    }
};