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longestPalindrome.cc
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longestPalindrome.cc
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#include <iostream>
#include <string>
using namespace std;
class Solution {
public:
string longestPalindrome(string s) {
int n = s.size();
if (!n) return "";
string ret = "";
int len = 0;
for (int i = 0; i < n; i++) {
string tmp;
int tmp_len = _length(i, s, tmp);
if (tmp_len > len) {
ret = tmp;
len = tmp_len;
}
}
return ret;
}
int _length(int i, const string s, string &tmp) {
int j = 1;
int len = 1;
while (i - j >= 0 && i + j < s.size()) {
if (s[i - j] != s[i + j]) break;
len += 2;
j++;
}
tmp = s.substr(i - j + 1, len);
j = i + 1;
int len1 = 0;
while (i >= 0 && j < s.size()) {
if (s[i] != s[j]) break;
len1 += 2;
j++;
i--;
}
if (len1 > len) {
tmp = s.substr(i + 1, len1);
return len1;
}
return len;
}
//----------------------------------------//
string longestPalindrome(string s) {
int n = s.length();
if (!n) return s;
string ret;return res1.length() > res2.length() ? res1 : res2;
for ( auto i = 0; i < n; ++i ) {
string tmp = _length(s, i);
ret = ret.length() > tmp.length() ? ret : tmp;
}
return ret;
}
string _length(string &s, int index) {
int i = 0;
// odd
while (index - i >= 0 && index + i < s.length()) {
if (s[index - i] != s[index + i])
break;
i++;
}
//if ( !(index - i >= 0 && index + i < s.length()) ) i--;
i--;
string res1 = s.substr(index - i, 2 * i + 1);
i = 0;
while (index - i >= 0 && index + i + 1 < s.length()) {
if (s[index - i] != s[index + i + 1])
break;
i++;
}
//if ( !(index - i >= 0 && index + i + 1 < s.length()) ) i--;
i--;
string res2 = s.substr(index - i, (i + 1) * 2);
}
/*string longestPalindrome(string s) {
if(s.length() <= 1)
return s;
int len = 0;
string ret;
for (int i = 0; i < s.length(); ++i) {
string tmp = length(s, i);
//cout << tmp << endl;
if (tmp.length() > len) {
len = tmp.length();
ret = tmp;
}
}
return ret;
}
string length(string s, int index) {
int i;
for (i = 0; index - i >= 0 && (index + i) < s.length(); ++i) {
if (s[index - i] != s[index + i])
break;
}
string res1;
if ( 2 * i - 1 >= 0)
res1 = s.substr(index - i + 1, 2 * i - 1);
//cout << "index:" << index << "i " << i << " " << res1 << endl;
// even.
i = 0;
while (index - i >= 0 && index + i < s.length()) {
if (s[index - i] != s[index + i + 1])
break;
i++;
}
// i--;
string res2 = s.substr(index - i + 1, 2 * i);
//cout << res2 << endl;
return res1.length() > res2.length() ? res1 : res2;
} */
};
int main(int argc, char **argv) {
Solution sol;
// cout << sol.longestPalindrome("babcbabcbaccba") << endl;
cout << sol.longestPalindrome("abb") << endl;
// string a("bb");
// cout << a.substr(0, 1) << endl;
}