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35 lines (29 loc) · 867 Bytes
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Copy path214.cpp
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35 lines (29 loc) · 867 Bytes
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class Solution {
public:
bool isPalindrome(const string& s) {
if (s.empty()) return true;
int i = 0;
int j = s.size() - 1;
while (i < j) {
if (s[i] != s[j]) return false;
i++;
j--;
}
return true;
}
string shortestPalindrome(string s) {
if (s.empty()) return s;
// 边界：如果s本身是回文串，直接返回s本身
if (isPalindrome(s)) return s;
// 否则，从倒数第2个字符开始找s前面最长的回文串
for (int j = s.size() - 2; j >= 0; j--) {
string s1 = s.substr(0, j+1);
if (isPalindrome(s1)) {
string s2 = s.substr(j+1);
std::reverse(s2.begin(), s2.end());
return s2 + s;
}
}
return s;
}
};