Manacher
说明
manacher算法能在接近线性的时间找到最长的回文串。
推荐一篇博客,看这篇博客看了三四次才把这个算法给搞明白->Manacher's Algorithm 马拉车算法
使用方法
string subStr = Manacher(string s);
返回值为最长回文串
模版
#include <vector>
#include <iostream>
#include <string>
using namespace std;
string Manacher(string s) {
// Insert '#'
string t = "$#";
for (int i = 0; i < s.size(); ++i) {
t += s[i];
t += "#";
}
// Process t
vector<int> p(t.size(), 0);
int mx = 0, id = 0, resLen = 0, resCenter = 0;
for (int i = 1; i < t.size(); ++i) {
p[i] = mx > i ? min(p[2 * id - i], mx - i) : 1;
while (t[i + p[i]] == t[i - p[i]]) ++p[i];
if (mx < i + p[i]) {
mx = i + p[i];
id = i;
}
if (resLen < p[i]) {
resLen = p[i];
resCenter = i;
}
}
return s.substr((resCenter - resLen) / 2, resLen - 1);
}
int main() {
string s1 = "12212";
cout << Manacher(s1) << endl;
string s2 = "122122";
cout << Manacher(s2) << endl;
string s = "waabwswfd";
cout << Manacher(s) << endl;
}