【leetcode】438. Find All Anagrams in a String

problem

438. Find All Anagrams in a String

solution1:

class Solution {
public:
    vector<int> findAnagrams(string s, string p) {
        if(s.empty()) return {};
        vector<int> res, pv(256, 0);
        for(auto a:p) pv[a]++;
        int sn = s.size();
        int i = 0;
        while(i<sn)
        {
            vector<int> tmp = pv;
            bool is = true;
            for(int j=i; j<i+p.size(); j++)
            {
                if(--tmp[s[j]]<0)
                {
                    is = false;
                    break;
                }
            }
            if(is) res.push_back(i);
            i++;
        }
        return res;
    }
};

solution2:使用哈希表表示一定字符长度内各个字符的个数，每次滑窗需要添加最新的字符，且减去最旧的字符，然后比较哈希表。

class Solution {
public:
    vector<int> findAnagrams(string s, string p) {
        if(s.empty()) return{};
        vector<int> res, m1(256, 0), m2(256, 0);
        for(int i=0; i<p.size(); i++)
        {
            m1[p[i]]++;
            m2[s[i]]++;
        }
        if(m1==m2) res.push_back(0);
        for(int i=p.size(); i<s.size(); i++)
        {
            m2[s[i]]++;
            m2[s[i-p.size()]]--;
            if(m1==m2) res.push_back(i-p.size()+1);
        }
        return res;
        
    }
};

参考

1. Leetcode_438. Find All Anagrams in a String;

完