|
| 1 | +#include <bits/stdc++.h> |
| 2 | +#define ll long long |
| 3 | +using namespace std; |
| 4 | + |
| 5 | +struct ranking { |
| 6 | + ll index; |
| 7 | + ll first; |
| 8 | + ll second; |
| 9 | +}; |
| 10 | + |
| 11 | +bool comp(ranking a, ranking b) { |
| 12 | + if (a.first == b.first) { |
| 13 | + return a.second < b.second; |
| 14 | + } |
| 15 | + return a.first < b.first; |
| 16 | +} |
| 17 | + |
| 18 | +vector<ll> build_suffix_array(string s) { |
| 19 | + const ll n = s.length(); |
| 20 | + const ll lgn = ceil(log2(n)); |
| 21 | + |
| 22 | + // vector to hold final suffix array result |
| 23 | + vector<ll> sa(n); |
| 24 | + |
| 25 | + // P[i][j] holds the ranking of the j-th suffix |
| 26 | + // after comparing the first 2^i characters |
| 27 | + // of that suffix |
| 28 | + ll P[lgn][n]; |
| 29 | + |
| 30 | + // vector to store ranking tuples of suffixes |
| 31 | + vector<ranking> ranks(n); |
| 32 | + |
| 33 | + ll i, j, step = 1; |
| 34 | + for(j = 0; j < n; j++) { |
| 35 | + P[0][j] = s[j] - 'a'; |
| 36 | + } |
| 37 | + |
| 38 | + for(i = 1; i <= lgn; i++, step++) { |
| 39 | + for(j = 0; j < n; j++) { |
| 40 | + ranks[j].index = j; |
| 41 | + ranks[j].first = P[i-1][j]; |
| 42 | + ranks[j].second = (j + pow(2,i-1) < n) ? P[i-1][j + (ll)(pow(2,i-1))] : -1; |
| 43 | + } |
| 44 | + |
| 45 | + sort(ranks.begin(), ranks.end(), comp); |
| 46 | + |
| 47 | + for(j = 0; j < n; j++) { |
| 48 | + P[i][ranks[j].index] = (j > 0 && ranks[j].first == ranks[j-1].first && ranks[j].second == ranks[j-1].second) ? P[i][ranks[j-1].index] : j; |
| 49 | + } |
| 50 | + } |
| 51 | + |
| 52 | + step -= 1; |
| 53 | + |
| 54 | + for(i = 0; i < n; i++) { |
| 55 | + sa[P[step][i]] = i; |
| 56 | + } |
| 57 | + |
| 58 | + return sa; |
| 59 | +} |
| 60 | + |
| 61 | +int main() { |
| 62 | + string s; |
| 63 | + cin >> s; |
| 64 | + vector<ll> sa = build_suffix_array(s); |
| 65 | + for(ll i = 0; i < s.length(); i++) { |
| 66 | + cout << i << " : " << sa[i] << endl; |
| 67 | + } |
| 68 | + return 0; |
| 69 | +} |
0 commit comments