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94_最长回文字符串.cpp
69 lines (57 loc) · 1.58 KB
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94_最长回文字符串.cpp
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#include <iostream>
#include <cstring>
#include <vector>
#include <algorithm>
using namespace std;
string longestPalindrome(string str) {
if (str.size() == 0) {
return string();
}
string charArr = "$#";
for (int i = 0; i < str.size(); ++i) {
charArr += str[i];
charArr += "#";
}
vector<int> pArr(charArr.size());
int pR = -1;
int index = -1;
int resCenter = -1;
int reslen = -1;
for (int i = 0; i < charArr.size(); i++) {
pArr[i] = pR > i ? min(pArr[2 * index - i], pR - i) : 1;
while (i + pArr[i] < charArr.size() && i - pArr[i] > -1) {
if (charArr[i + pArr[i]] == charArr[i - pArr[i]])
pArr[i]++;
else {
break;
}
}
if (i + pArr[i] > pR) {
pR = i + pArr[i];
index = i;
}
if (reslen < pArr[i]) {
reslen = pArr[i];
resCenter = i;
}
if (pR == charArr.size()) {
break;
}
}
return str.substr((resCenter - reslen) / 2, reslen - 1);
}
int main() {
string s1 = "12212";
cout << s1.c_str() << endl;
cout << longestPalindrome(s1).c_str() << endl;
cout << "=======================" << endl;
string s2 = "122122";
cout << s2.c_str() << endl;
cout << longestPalindrome(s2).c_str() << endl;
cout << "=======================" << endl;
string s3 = "waabwswfd";
cout << s3.c_str() << endl;
cout << longestPalindrome(s3).c_str() << endl;
cout << "=======================" << endl;
return 0;
}