leetcode-438-Find All Anagrams in a String
阿新 • • 發佈:2018-04-22
IT -- 新的 iss HA nag cpp mat strings
題目描述:
Given a string s and a non-empty string p, find all the start indices of p‘s anagrams in s.
Strings consists of lowercase English letters only and the length of both strings s and p will not be larger than 20,100.
The order of output does not matter.
Example 1:
Input: s: "cbaebabacd" p: "abc" Output: [0, 6] Explanation: The substring with start index = 0 is "cba", which is an anagram of "abc". The substring with start index = 6 is "bac", which is an anagram of "abc".
Example 2:
Input:
s: "abab" p: "ab"
Output:
[0, 1, 2]
Explanation:
The substring with start index = 0 is "ab", which is an anagram of "ab".
The substring with start index = 1 is "ba", which is an anagram of "ab".
The substring with start index = 2 is "ab", which is an anagram of "ab".
要完成的函數:
vector<int> findAnagrams(string s, string p)
說明:
1、給定一個字符串s和非空字符串p,將p中元素不斷交換形成一個新的字符串,如果這個新的字符串在s中能找到匹配的,那麽就輸出匹配到的開始的位置,直到處理到字符串s結束。
2、這道題目難道要記住p經過交換可能形成的所有字符串嗎,難道再類似於滑動窗口一般不斷在s中比較?
其實不用記住所有字符串,記住p經過交換可能形成的所有字符串其實等價於記住p中所有字母出現的次數。
所以代碼如下:
vector<int> findAnagrams(string s, string p)
{
vector<int>res;
vector <int>p1(26,0);
vector<int>s1(26,0);
for(int i=0;i<p.size();i++)
{
p1[p[i]-‘a‘]++;
}
for(int i=0;i<p.size();i++)
{
s1[s[i]-‘a‘]++;
}
if(s.size()<p.size())
return res;
if(p1==s1)
res.push_back(0);
for(int i=1;i<=s.size()-p.size();i++)
{
s1[s[i-1]-‘a‘]--;//當窗口滑動時,s1中要減去窗口前一位的字母1次
s1[s[i-1+p.size()]-‘a‘]++;//s1要加上窗口最後新的一維的字母1次
if(s1==p1)
res.push_back(i);
}
return res;
}
上述代碼實測35ms,beats 90.84% of cpp submissions。
leetcode-438-Find All Anagrams in a String