LeetCode Substring with Concatenation of All Words, leetcode
You are given a string, S, and a list of words, L, that are all of the same length. find all starting indices of substring (s) in S that is a concatenation of each word in L exactly once and without any intervening characters.
For example, given:
S:"barfoothefoobarman"
L:["foo", "bar"]
You shoshould return the indices:[0,9]
.
(Order does not matter ).
Locate the starting point of the substring that appears in all strings in string S, and the sequence of occurrence can be unordered.
Idea: it is a question for maintaining a dynamic window and maintaining a [start, end) window to contain strings in L, every moving unit is len (L strings are of the same size)
class Solution {public: vector<int> findSubstring(string S, vector<string> &L) { map<string, int> wordTimes; for (int i = 0; i < L.size(); i++) { if (wordTimes.count(L[i]) == 0) wordTimes[L[i]] = 1; else wordTimes[L[i]]++; } int len = L[0].size(); vector<int> res; for (int i = 0; i < len; i++) { map<string, int> curTimes; int start = i, cnt = 0; for (int end = i; end <= (int)S.size()-len; end += len) { string word = S.substr(end, len); if (wordTimes.find(word) != wordTimes.end()) { if (curTimes.find(word) == curTimes.end()) curTimes[word] = 1; else curTimes[word]++; if (curTimes[word] <= wordTimes[word]) cnt++; else { for (int k = start; ; k += len) { string tmp = S.substr(k, len); curTimes[tmp]--; if (tmp == word) { start = k + len; break; } cnt--; } } if (cnt == L.size()) res.push_back(start); } else { start = end + len; curTimes.clear(); cnt = 0; } } } return res; }};