#include <bits/stdc++.h> using namespace std; char s[300010]; int n; struct data { int link, len, cnt; int nxt[26]; data () { link = len = cnt = 0; memset(nxt, 0, sizeof nxt); } } a[300010]; int last; int node; vector <int> g[300010]; int sub[300010]; long long opt; void dfs(int x) { sub[x] = a[x].cnt; for(auto i : g[x]) { dfs(i); sub[x] += sub[i]; } opt = max(opt, 1LL * sub[x] * a[x].len); } void addChar(int idx) { int c = s[idx] - 'a'; int cur = last; while(true) { int len = a[cur].len; if(idx - len - 1 >= 0 && s[idx - len - 1] == s[idx]) { break; } cur = a[cur].link; } if(a[cur].nxt[c] != 0) { last = a[cur].nxt[c]; a[last].cnt += 1; return ; } last = ++node; a[node].len = a[cur].len + 2; a[cur].nxt[c] = node; a[node].cnt += 1; if(a[node].len == 1) { a[node].link = 2; return ; } while(true) { cur = a[cur].link; int len = a[cur].len; if(idx - len - 1 >= 0 && s[idx - len - 1] == s[idx]) { a[node].link = a[cur].nxt[c]; break; } } return ; } void initTree() { node = 2; last = 2; a[1].len = -1; a[2].len = 0; a[1].link = 1; a[2].link = 1; } int main() { scanf("%s", s); n = strlen(s); initTree(); for(int i = 0; i < n; i++) { addChar(i); } for(int i = 2; i <= node; i++) { g[a[i].link].push_back(i); } dfs(1); printf("%lld\n", opt); return 0; }

palindrome.cpp: In function 'int main()':
palindrome.cpp:66:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%s", s);
     ~~~~~^~~~~~~~~