Submission #13161

#	Time	Username	Problem	Language	Result	Execution time	Memory
13161		gs14004	Palindromes (APIO14_palindrome)	C++14	23 / 100	162 ms	23348 KiB

palindrome

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef pair<int,int> pi;

char str[600005];
int n;
int dp[600005];

void manacher(){
    int max_val = 0, pos = 0;
    for (int i=1; i<=n; i++) {
        int ret = i;
        if(max_val >= i){
            ret = min(max_val,i + dp[2 * pos - i]);
        }
        while (ret+1<=n && 2*i-ret-1> 0 && str[ret+1] == str[2*i-ret-1]){
            ret++;
        }
        dp[i] = ret - i;
        if(ret > max_val){
            pos = i, ret = max_val;
        }
    }
    for (int i=1; i<=n; i++) {
        if(i%2 == 0) dp[i]++;
        dp[i] /= 2;
    }
}

const int prime = 1e9 + 9;
long long hs[300005], pw[300005];

unordered_map<long long,int> len, cnt, num;
unordered_map<long long,long long> nxt;
vector<long long> hash_candidate;

int piv;

long long get_hash(int s, int e){
    return hs[e] - hs[s-1] * pw[e - s + 1];
}

void shrink(int s, int e, long long pa){
    if(s > e) return;
    long long par = 0;
    num[0] = 0;
    cnt[get_hash(s,e)]++;
    while (s <= e) {
        long long hsh = get_hash(s,e);
        hash_candidate.push_back(hsh);
        if(par) nxt[par] = hsh;
        if(len.find(hsh) == len.end()){
            len[hsh] = e - s + 1;
            num[hsh] = ++piv;
        }
        else break;
        par = hsh;
        s++;
        e--;
    }
}

int tpar[300005], tcnt[300005], tlen[300005];
vector<int> graph[300005];
int subsize[300005];
long long ret;

int dfs(int x, int pa){
    int r = tcnt[x];
    for (int i=0; i<graph[x].size(); i++) {
        if(graph[x][i] == pa) continue;
        r += dfs(graph[x][i],x);
    }
    subsize[x] = r;
   // printf("%d %d\n",subsize[x],tlen[x]);
    ret = max(ret,1ll * subsize[x] * tlen[x]);
    return r;
}

void make_tree(){
    for (long long i : hash_candidate){
        tpar[num[i]] = num[nxt[i]];
        tcnt[num[i]] = cnt[i];
        tlen[num[i]] = len[i];
    }
    for (int i=0; i<=piv; i++) {
        if (i == tpar[i]) continue;
        graph[i].push_back(tpar[i]);
        graph[tpar[i]].push_back(i);
    }
    dfs(0,-1);
}

int main(){
    scanf("%s",str);
    n = (int)strlen(str);
    for (int i=n-1; i>=0; i--) {
        str[2*i+1] = str[i];
        str[2*i] = ' ';
    }
    n = 2 * n - 1;
    str[0] = 0;
    manacher();
    pw[0] = 1;
    for (int i=1; i<=(n+1)/2; i++) {
        hs[i] = hs[i-1] * prime + str[2*i-1];
        pw[i] = pw[i-1] * prime;
    }
    for (int i=1; i<=n; i++) {
        if(i % 2 == 1){
            shrink((i+1)/2 - dp[i],(i+1)/2 + dp[i],0);
        }
        else{
            shrink(i/2 + 1 - dp[i], i/2 + dp[i],0);
        }
    }
    make_tree();
    printf("%lld",ret);
}

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 26
• Subtask 5: 0 / 27