This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <bits/stdc++.h>
#define PRINT(x) cerr<<#x<<'='<<x<<endl;
using namespace std;
struct PalTree {
#define P_SIGMA 26
#define FIRST_NODE 1
#define SECOND_NODE 2
struct Node {
int len, cnt, dub, slink;
int to[P_SIGMA];
Node() { len = cnt = dub = slink = 0; for(int i = 0; i < P_SIGMA; i++) to[i] = 0; }
Node(int _len, int _cnt, int _dub, int _slink) {
len = _len; cnt = _cnt; dub = _dub; slink = _slink;
for(int i = 0; i < P_SIGMA; i++) to[i] = 0;
}
};
string s;
vector<Node> pt;
int suff;
int toidx(char c) { return c-'a'; }
void addLetter(char c) {
s += c; int len = s.size();
while(c != s[len-2-pt[suff].len]) {
suff = pt[suff].slink;
}
int nd = pt[suff].to[toidx(c)];
if(nd == 0) {
nd = pt.size();
pt[suff].to[toidx(c)] = nd;
pt.push_back(Node(pt[suff].len+2, 0, 0, 0));
if(suff == FIRST_NODE) {
pt[nd].slink = SECOND_NODE;
} else {
int u = pt[suff].slink;
while(c != s[len-2-pt[u].len]) {
u = pt[u].slink;
}
pt[nd].slink = pt[u].to[toidx(c)];
}
pt[nd].dub = pt[pt[nd].slink].dub+1;
}
pt[nd].cnt++;
suff = nd;
}
void calcCnt() {
for(int i = pt.size()-1; i > 2; i--) {
pt[pt[i].slink].cnt += pt[i].cnt;
}
}
void init() {
pt.clear();
s = "";
suff = 2;
pt.push_back(Node(0, 0, 0, 0));
pt.push_back(Node(-1, 0, 0, FIRST_NODE)); ///first node
pt.push_back(Node(0, 0, 0, FIRST_NODE)); ///second node
}
Node &operator[](int idx) {
if(idx >= pt.size()) {
cerr << "Index out of bounds" <<endl;
return pt[0];
}
return pt[idx];
}
};
PalTree pt;
int main() {
ios::sync_with_stdio(false); cin.tie(0);
string s; cin >> s;
pt.init();
for(auto x : s) {
pt.addLetter(x);
}
pt.calcCnt();
long long rez = 0;
for(int i = pt.pt.size()-1; i > 2; i--) {
rez = max(rez, (long long) pt[i].len*pt[i].cnt);
}
cout << rez << endl;
return 0;
}
Compilation message (stderr)
palindrome.cpp: In member function 'PalTree::Node& PalTree::operator[](int)':
palindrome.cpp:60:16: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<PalTree::Node>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
60 | if(idx >= pt.size()) {
| ~~~~^~~~~~~~~~~~
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