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336.cpp
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336.cpp
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class Solution {
public:
bool isPalindrome(string& s, int left, int right) {
while (left < right) {
if (s[left] != s[right]) return false;
left++;
right--;
}
return true;
}
vector<vector<int>> palindromePairs(vector<string>& words) {
vector<vector<int>> res;
unordered_map<string, int> word2idx;
set<int> sizeSt;
for (int i = 0; i < words.size(); ++i) {
word2idx[words[i]] = i;
sizeSt.insert(words[i].size());
}
for (int i = 0; i < words.size(); ++i) {
string t = words[i];
reverse(t.begin(), t.end());
if (word2idx.find(t) != word2idx.end() && word2idx[t] != i) {
res.push_back({i, word2idx[t]});
}
int length = t.size();
auto maxIt = sizeSt.find(length);
for (auto it = sizeSt.begin(); it != maxIt; ++it) {
int subLen = *it;
string subRight = t.substr(length - subLen);
if (isPalindrome(t, 0, length - subLen - 1) && word2idx.find(subRight) != word2idx.end()) {
res.push_back({i, word2idx[subRight]});
}
string subLeft = t.substr(0, subLen);
if (isPalindrome(t, subLen, length - 1) && word2idx.find(subLeft) != word2idx.end()) {
res.push_back({word2idx[subLeft], i});
}
}
}
return res;
}
};