Submission #223283

#	Time	Username	Problem	Language	Result	Execution time	Memory
223283		cheeheng	Lampice (COCI19_lampice)	C++14	17 / 110	220 ms	98424 KiB

lampice

#include <bits/stdc++.h>
using namespace std;

char S[50005];

vector<int> AdjList[50005];

const long long MOD = (1LL<<55)-3;

long long pow26[50005];

long long dist[3005][3005];
int dist2[3005][3005];

int main(){
    int N;
    scanf("%d", &N);

    assert(MOD%13 != 0);

    pow26[0] = 1;
    for(int i = 1; i <= N; i ++){
        pow26[i] = pow26[i-1]*26%MOD;
    }

    for(int i = 1; i <= N; i ++){
        scanf(" %c", &S[i]);
    }

    bool subtask2 = true;
    for(int i = 1; i < N; i ++){
        int a, b;
        scanf("%d%d", &a, &b);
        AdjList[a].push_back(b);
        AdjList[b].push_back(a);
        if(a == i && b == i+1 || b == i && a == i+1){
        }else{
            subtask2 = false;
        }
    }

    if(N <= 3000){
        int ans = 0;
        memset(dist, -1, sizeof(dist));
        for(int i = 1; i <= N; i ++){
            queue<int> q;
            q.push(i);
            dist[i][i] = S[i]-'a';
            dist2[i][i] = 0;
            while(!q.empty()){
                int u = q.front(); q.pop();
                for(int v: AdjList[u]){
                    if(dist[i][v] == -1){
                        dist[i][v] = (26*dist[i][u] + (S[v]-'a'))%MOD;
                        dist2[i][v] = dist2[i][u]+1;
                        q.push(v);
                    }
                }
            }
        }

        for(int i = 1; i <= N; i ++){
            for(int j = i; j <= N; j ++){
                //printf("%d %d %lld %lld\n", i, j, dist[i][j], dist[j][i]);
                assert(dist[i][j] != -1);
                if(dist[i][j] == dist[j][i]){
                    ans = max(ans, 1+dist2[i][j]);
                }
            }
        }

        printf("%d", ans);
        return 0;
    }

    /*if(subtask2){
        int ans = 0;
        for(int i = 1; i <= N; i ++){
            long long forward1 = 0;
            long long backward1 = 0;

            for(int j = i; j <= N; j ++){
                forward1 = (forward1*26+(S[j]-'0'))%MOD;

                backward1 += pow26[j-i]*(S[j]-'0');
                backward1 %= MOD;

                if(forward1 == backward1){
                    ans = max(ans, j-i+1);
                }
            }
        }
        printf("%d", ans);
        return 0;
    }*/

    return 0;
}

Compilation message (stderr)

lampice.cpp: In function 'int main()':
lampice.cpp:36:19: warning: suggest parentheses around '&&' within '||' [-Wparentheses]
         if(a == i && b == i+1 || b == i && a == i+1){
            ~~~~~~~^~~~~~~~~~~
lampice.cpp:30:10: warning: variable 'subtask2' set but not used [-Wunused-but-set-variable]
     bool subtask2 = true;
          ^~~~~~~~
lampice.cpp:17:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &N);
     ~~~~~^~~~~~~~~~
lampice.cpp:27:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf(" %c", &S[i]);
         ~~~~~^~~~~~~~~~~~~~
lampice.cpp:33:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &a, &b);
         ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 17 / 17
• Subtask 2: 0 / 25
• Subtask 3: 0 / 31
• Subtask 4: 0 / 37