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Submission #71865

# Submission time Handle Problem Language Result Execution time Memory
71865 2018-08-25T17:31:44 Z evpipis Palindromes (APIO14_palindrome) C++14
100 / 100
 973 ms 61544 KB 
#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define mp make_pair
#define pb push_back
typedef long long ll;
typedef pair<int, int> ii;

const int len = 3e5+5, mod = 1e9+7, base = 57;
int suf[len], has1[len], has2[len], po[len], lim[len], n, lef[len], rig[len];
int tmp[len], ran[len], cnt[len];
char str[len];
vector<int> vec[len];
vector<ii> st;
set<int> mys;

inline int add(int a, int b){
    a += b;
    if (a >= mod) a -= mod;
    return a;
}

inline int sub(int a, int b){
    a -= b;
    if (a < 0) a += mod;
    return a;
}

int mul(int a, int b){
    return (a*1LL*b)%mod;
}

inline int val1(int l, int r){
    l++, r++;
    return sub(has1[r], mul(has1[l-1], po[r-l+1]));
}

inline int val2(int l, int r){
    return (sub(has2[l], mul(has2[r+1], po[r-l+1])));
}

int lcp(int a, int b){
    int l = 1, r = n-1-max(a, b)+1, ans = 0;
    while (l <= r){
        int mid = (l+r)/2;
        if (val1(a, a+mid-1) == val1(b, b+mid-1))
            ans = mid, l = mid+1;
        else
            r = mid-1;
    }

    return ans;
}

int bs(int i, int t){
    int l = 1, r = min(n-i-t, i+1), ans = 0;
    while (l <= r){
        int mid = (l+r)/2;
        if (val1(i-mid+1, i+t+mid-1) == val2(i-mid+1, i+t+mid-1))
            ans = 2*mid - (1-t), l = mid+1;
        else
            r = mid-1;
    }

    return ans;
}

void radix(int k){
    for (int i = 0; i <= max(n, 300); i++)
        cnt[i] = 0;
    for (int i = 0; i < n; i++)
        cnt[(suf[i]+k<n?ran[suf[i]+k]:0)+1]++;
    for (int i = 1; i <= max(n, 300); i++)
        cnt[i] += cnt[i-1];

    for (int i = 0; i < n; i++)
        tmp[cnt[(suf[i]+k<n?ran[suf[i]+k]:0)]++] = suf[i];
    for (int i = 0; i < n; i++)
        suf[i] = tmp[i];
}

int main(){
    scanf("%s", &str);
    n = strlen(str);
    str[n++] = 0;

    po[0] = 1;
    for (int i = 1; i <= n; i++)
        po[i] = mul(po[i-1], base);
    for (int i = 1; i <= n; i++)
        has1[i] = add(mul(has1[i-1], base), str[i-1]-'a');
    for (int i = n-1; i >= 0; i--)
        has2[i] = add(mul(has2[i+1], base), str[i]-'a');

    for (int i = 0; i < n; i++)
        suf[i] = i;
    //sort(suf, suf+n, comp); // suffix array before :(

    for (int i = 0; i < n; i++)
        ran[i] = str[i];
    for (int k = 1; k <= n; k*=2){
        radix(k);
        radix(0);

        int ptr = -1;
        for (int i = 0; i < n; i++){
            if (i == 0 || ran[suf[i]] != ran[suf[i-1]] || ran[suf[i]+k] != ran[suf[i-1]+k])
                tmp[suf[i]] = ++ptr;
            else
                tmp[suf[i]] = ptr;
        }

        for (int i = 0; i < n; i++)
            ran[i] = tmp[i];

        if (ptr == n-1) break;
    }

    for (int i = 0; i < n; i++)
        lim[i] = -1;
    for (int i = 0; i < n-1; i++)
        lim[suf[i]] = lcp(suf[i], suf[i+1]);

    //for (int i = 0; i < n; i++)
      //  printf("%d ", suf[i]);
    //printf("\n");

    ll ans = 0;
    for (int i = 0; i < n; i++){
        int temp = bs(i, 0);
        vec[i-temp/2].pb(temp);
        ans = max(ans, (ll)temp);

        //printf("i = %d, mx0 = %d\n", i, temp);

        temp = bs(i, 1);
        vec[i-temp/2+1].pb(temp);
        ans = max(ans, (ll)temp);

        //printf("i = %d, mx1 = %d\n", i, temp);
    }

    int k = 0;
    for (int i = 0; i < n; i++){
        for (int j = 0; j < vec[i].size(); j++)
            mys.insert(vec[i][j]-k);

        set<int>::iterator it = mys.upper_bound(lim[i]-k);
        if (lim[i] != -1 && it != mys.begin()){
            it = prev(it);
            lim[i] = *it + k;
        }
        else
            lim[i] = 0;

        k-=2;
    }

    //for (int i = 0; i < n-1; i++)
      //  printf("%d ", lim[suf[i]]);
    //printf("\n");

    st.pb(mp(-1, -1));
    for (int i = 0; i < n-1; i++){
        while (lim[suf[i]] <= st.back().fi)
            st.pop_back();
        lef[i] = st.back().se;
        st.pb(mp(lim[suf[i]], i));
    }

    st.clear(), st.pb(mp(-1, n-1));
    for (int i = n-2; i >= 0; i--){
        while (lim[suf[i]] <= st.back().fi)
            st.pop_back();
        rig[i] = st.back().se;
        st.pb(mp(lim[suf[i]], i));
    }

    for (int i = 0; i < n-1; i++)
        ans = max(ans, lim[suf[i]] * 1LL * (rig[i]-lef[i]));
    printf("%lld\n", ans);
    return 0;
}

Compilation message

palindrome.cpp: In function 'int main()':
palindrome.cpp:85:21: warning: format '%s' expects argument of type 'char*', but argument 2 has type 'char (*)[300005]' [-Wformat=]
     scanf("%s", &str);
                 ~~~~^
palindrome.cpp:147:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for (int j = 0; j < vec[i].size(); j++)
                         ~~^~~~~~~~~~~~~~~
palindrome.cpp:85:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%s", &str);
     ~~~~~^~~~~~~~~~~~

Subtask #1
8.0 / 8.0

# Verdict Execution time Memory Grader output
1 Correct 10 ms 7416 KB Output is correct
2 Correct 9 ms 7416 KB Output is correct
3 Correct 12 ms 7452 KB Output is correct
4 Correct 10 ms 7500 KB Output is correct
5 Correct 10 ms 7552 KB Output is correct
6 Correct 9 ms 7584 KB Output is correct
7 Correct 8 ms 7584 KB Output is correct
8 Correct 10 ms 7588 KB Output is correct
9 Correct 9 ms 7588 KB Output is correct
10 Correct 8 ms 7608 KB Output is correct
11 Correct 8 ms 7632 KB Output is correct
12 Correct 8 ms 7632 KB Output is correct
13 Correct 10 ms 7632 KB Output is correct
14 Correct 8 ms 7632 KB Output is correct
15 Correct 8 ms 7632 KB Output is correct
16 Correct 10 ms 7632 KB Output is correct
17 Correct 9 ms 7632 KB Output is correct
18 Correct 8 ms 7632 KB Output is correct
19 Correct 8 ms 7692 KB Output is correct
20 Correct 9 ms 7692 KB Output is correct
21 Correct 8 ms 7692 KB Output is correct
22 Correct 10 ms 7692 KB Output is correct
23 Correct 9 ms 7692 KB Output is correct
24 Correct 8 ms 7780 KB Output is correct
25 Correct 11 ms 7780 KB Output is correct
26 Correct 14 ms 7780 KB Output is correct
27 Correct 11 ms 7780 KB Output is correct
28 Correct 9 ms 7780 KB Output is correct
29 Correct 9 ms 7780 KB Output is correct
30 Correct 8 ms 7780 KB Output is correct
31 Correct 9 ms 7780 KB Output is correct
32 Correct 12 ms 7780 KB Output is correct

Subtask #2
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 11 ms 7788 KB Output is correct
2 Correct 10 ms 7788 KB Output is correct
3 Correct 9 ms 7860 KB Output is correct
4 Correct 9 ms 7884 KB Output is correct
5 Correct 9 ms 7884 KB Output is correct
6 Correct 11 ms 7916 KB Output is correct
7 Correct 11 ms 7916 KB Output is correct
8 Correct 11 ms 7916 KB Output is correct
9 Correct 12 ms 7916 KB Output is correct
10 Correct 12 ms 7916 KB Output is correct
11 Correct 9 ms 7916 KB Output is correct
12 Correct 12 ms 7916 KB Output is correct

Subtask #3
24.0 / 24.0

# Verdict Execution time Memory Grader output
1 Correct 22 ms 9468 KB Output is correct
2 Correct 22 ms 9468 KB Output is correct
3 Correct 22 ms 9596 KB Output is correct
4 Correct 23 ms 9596 KB Output is correct
5 Correct 21 ms 9596 KB Output is correct
6 Correct 21 ms 9596 KB Output is correct
7 Correct 23 ms 9596 KB Output is correct
8 Correct 22 ms 9596 KB Output is correct
9 Correct 19 ms 9596 KB Output is correct
10 Correct 22 ms 9596 KB Output is correct

Subtask #4
26.0 / 26.0

# Verdict Execution time Memory Grader output
1 Correct 255 ms 25096 KB Output is correct
2 Correct 195 ms 25096 KB Output is correct
3 Correct 202 ms 25584 KB Output is correct
4 Correct 226 ms 25584 KB Output is correct
5 Correct 240 ms 25584 KB Output is correct
6 Correct 223 ms 25584 KB Output is correct
7 Correct 209 ms 25584 KB Output is correct
8 Correct 194 ms 25584 KB Output is correct
9 Correct 274 ms 25584 KB Output is correct
10 Correct 196 ms 25584 KB Output is correct

Subtask #5
27.0 / 27.0

# Verdict Execution time Memory Grader output
1 Correct 727 ms 59184 KB Output is correct
2 Correct 628 ms 59184 KB Output is correct
3 Correct 672 ms 61544 KB Output is correct
4 Correct 695 ms 61544 KB Output is correct
5 Correct 787 ms 61544 KB Output is correct
6 Correct 643 ms 61544 KB Output is correct
7 Correct 690 ms 61544 KB Output is correct
8 Correct 613 ms 61544 KB Output is correct
9 Correct 630 ms 61544 KB Output is correct
10 Correct 785 ms 61544 KB Output is correct
11 Correct 681 ms 61544 KB Output is correct
12 Correct 973 ms 61544 KB Output is correct