kejpmdt's blog

By kejpmdt, history, 6 weeks ago, In English
#include <bits/stdc++.h>
using namespace std;
void radixsort(vector<pair<pair<int, int>, int>> &a)
{
    int n = a.size();
    {
        vector<int> cnt(n);
        for (auto x : a)
        {
            cnt[x.first.second]++;
        }
        vector<pair<pair<int, int>, int>> a_new(n);
        vector<int> pos(n);
        pos[0] = 0;
        for (int i = 1; i <= n; ++i)
        {
            pos[i] = pos[i - 1] + cnt[i - 1];
        }
        for (auto x : a)
        {
            int i = x.first.second;
            a_new[pos[i]] = x;
            pos[i]++;
        }
        a = a_new;
    }
    {
        vector<int> cnt(n);
        for (auto x : a)
        {
            cnt[x.first.first]++;
        }
        vector<pair<pair<int, int>, int>> a_new(n);
        vector<int> pos(n);
        pos[0] = 0;
        for (int i = 1; i <= n; ++i)
        {
            pos[i] = pos[i - 1] + cnt[i - 1];
        }
        for (auto x : a)
        {
            int i = x.first.first;
            a_new[pos[i]] = x;
            pos[i]++;
        }
        a = a_new;
    }
}
int main()
{
    string s;
    cin >> s;
    s += "$";
    int n = s.size();
    vector<int> p(n), c(n);
    {
        vector<pair<char, int>> a(n);
        for (int i = 0; i < n; ++i)
        {
            a[i] = {s[i], i};
        }
        sort(a.begin(), a.end());
        for (int i = 0; i < n; ++i)
        {
            p[i] = a[i].second;
        }
        c[p[0]] = 0;
        for (int i = 1; i < n; ++i)
        {
            if (a[i].first == a[i - 1].first)
            {
                c[p[i]] = c[p[i - 1]];
            }
            else
            {
                c[p[i]] = c[p[i - 1]] + 1;
            }
        }
    }
    int k = 0;
    while ((1 << k) < n)
    {
        vector<pair<pair<int, int>, int>> a(n);
        for (int i = 0; i < n; ++i)
        {
            a[i] = {{c[i], c[(i + (1 << k)) % n]}, i};
        }
        radixsort(a);
        for (int i = 0; i < n; ++i)
        {
            p[i] = a[i].second;
        }
        c[p[0]] = 0;
        for (int i = 1; i < n; ++i)
        {
            if (a[i].first == a[i - 1].first)
            {
                c[p[i]] = c[p[i - 1]];
            }
            else
            {
                c[p[i]] = c[p[i - 1]] + 1;
            }
        }
        k++;
    }
    for (int i = 0; i < n; ++i)
    {
        cout << p[i] << ' ';
    }
    return 0;
}

All of the probable error will be in the function called radixsort ,the other part doesn't have any error.

Could anyone tell me where the error is?

The original code could be found in the Suffix Array of the edu.

 
 
 
 
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6 weeks ago, # |
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for (int i = 1; i <= n; ++i)
{
    pos[i] = pos[i - 1] + cnt[i - 1];
}

One mistake i found was this:

Here size of pos is only $$$n$$$ so you cannot access $$$pos_n$$$