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- // lexicographic order for pairs
- inline bool leq(int a1, int a2, int b1, int b2) {
- return(a1 < b1 || a1 == b1 && a2 <= b2);
- }
- // and triples
- inline bool leq(int a1, int a2, int a3, int b1, int b2, int b3) {
- return(a1 < b1 || a1 == b1 && leq(a2,a3, b2,b3));
- } // and triples
- // stably sort a[0..n-1] to b[0..n-1] with keys in 0..K from r
- static void radixPass(int* a, int* b, int* r, int n, int K) {// count occurrences
- int* c = new int[K + 1]; // counter array
- for (int i = 0; i <= K; i++) c[i] = 0; // reset counters
- for (int i = 0; i < n; i++) c[r[a[i]]]++; // count occurrences
- for (int i = 0, sum = 0; i <= K; i++) // exclusive prefix sums
- {
- int t = c[i];
- c[i] = sum;
- sum += t;
- }
- for (int i = 0; i < n; i++) b[c[r[a[i]]]++] = a[i]; // sort
- delete [] c;
- }
- // find the suffix array SA of s[0..n-1] in {1..K}ˆn
- // require s[n]=s[n+1]=s[n+2]=0, n>=2
- void suffixArray(int* s, int* SA, int n, int K) {
- int n0 = (n+2)/3, n1 = (n+1)/3, n2 = n/3, n02 = n0+n2;
- int* s12 = new int[n02+3]; s12[n02] = s12[n02+1] = s12[n02+2] = 0;
- int* SA12 = new int[n02+3]; SA12[n02] = SA12[n02+1] = SA12[n02+2] = 0;
- int* s0 = new int[n0];
- int* SA0 = new int[n0];
- // generate positions of mod 1 and mod 2 suffixes
- // the "+(n0-n1)" adds a dummy mod 1 suffix if n%3 == 1
- for (int i=0, j=0; i < n + (n0-n1); i++)
- if (i%3 != 0) s12[j++] = i;
- // lsb radix sort the mod 1 and mod 2 triples
- radixPass(s12 , SA12, s+2, n02, K);
- radixPass(SA12, s12 , s+1, n02, K);
- radixPass(s12 , SA12, s , n02, K);
- // find lexicographic names of triples
- int name = 0, c0 = -1, c1 = -1, c2 = -1;
- for (int i = 0; i < n02; i++) {
- if (s[SA12[i]] != c0 || s[SA12[i]+1] != c1 || s[SA12[i]+2] != c2) {
- name++;
- c0 = s[SA12[i]];
- c1 = s[SA12[i]+1];
- c2 = s[SA12[i]+2];
- }
- if (SA12[i]%3 == 1) s12[SA12[i]/3] = name; // left half
- else s12[SA12[i]/3 + n0] = name; // right half
- }
- // recurse if names are not yet unique
- if (name < n02) {
- suffixArray(s12, SA12, n02, name);
- // store unique names in s12 using the suffix array
- for (int i = 0; i < n02; i++) s12[SA12[i]] = i + 1;
- } else // generate the suffix array of s12 directly
- for (int i = 0; i < n02; i++) SA12[s12[i] - 1] = i;
- // stably sort the mod 0 suffixes from SA12 by their first character
- for (int i = 0, j = 0; i < n02; i++)
- if (SA12[i] < n0) s0[j++] = 3*SA12[i];
- radixPass(s0, SA0, s, n0, K);
- // merge sorted SA0 suffixes and sorted SA12 suffixes
- for (int p = 0, t = n0-n1, k = 0; k < n; k++) {
- #define GetI() (SA12[t] < n0 ? SA12[t] * 3 + 1 : (SA12[t] - n0) * 3 + 2)
- int i = GetI(); // pos of current offset 12 suffix
- int j = SA0[p]; // pos of current offset 0 suffix
- if (SA12[t] < n0 ? // different compares for mod 1 and mod 2 suffixes
- leq(s[i], s12[SA12[t] + n0], s[j], s12[j/3]) :
- leq(s[i],s[i+1],s12[SA12[t]-n0+1], s[j],s[j+1],s12[j/3+n0]))
- {// suffix from SA12 is smaller
- SA[k] = i; t++;
- if (t == n02) // done --- only SA0 suffixes left
- for (k++; p < n0; p++, k++) SA[k] = SA0[p];
- } else {// suffix from SA0 is smaller
- SA[k] = j; p++;
- if (p == n0) // done --- only SA12 suffixes left
- for (k++; t < n02; t++, k++) SA[k] = GetI();
- }
- }
- delete [] s12; delete [] SA12; delete [] SA0; delete [] s0;
- }
- int main() {
- return 0;
- }
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