# "Go" HDU 6194 string string (2017 Shenyang webcast-suffix array)

Source: Internet
Author: User

Transferred from: http://blog.csdn.net/aozil_yang/article/details/77929216

Test instructions

Tells you a string and a K, to find out how many different substrings in this string happen to be k times.

Ideas:

An array of suffixes.

We first consider the substring that appears at least k times, so we enumerate the ordered suffix I (sa[i]).

Enumeration of K-segment K-segments.

Assuming that the current enumeration is Sa[i]~sa[i + k-1]

So let's say that the longest common prefix in this section is L.

Then there is a different substring of l at least k times.

We're going to subtract at least K + 1, but it has to do with the K-segment LCP, so it's definitely this paragraph looking up for a suffix or a suffix down.

i.e. Sa[i-1] ~ sa[i + k-1] and Sa[i] ~ sa[i + K] two times LCP minus can be.

But it's going to be much less.

The LCP which is obviously sa[i-1] ~ sa[i + k) is significantly reduced. Plus you can.

Note K =1 in the case of LCP will have a problem, that is, to find a string of the longest public prefix will have problems, a special sentence can be.

Must pay attention to boundary problem boundary problem boundary problem!!!

`1#include <cstdio>2#include <cstring>3#include <algorithm>4 using namespaceStd5 6 Const intMAXN = 100000 + 10;7 8 intT1[MAXN], T2[MAXN], C[MAXN];9 Ten BOOLcmpint* R,intAintBintL) { One     returnR[a] = = R[b] && r[a+l] = = R[b+l]; A} -  - voidDaintStr[],intSa[],intRank[],intLcp[],intNintm) { the++n; -     intI, J, p, *x = t1, *y = t2; -      for(i = 0; i < m; ++i) c[i] = 0; - //Puts ("HHA"); +      for(i = 0; i < n; ++i) c[x[i] = str[i]]++; -      for(i = 1; i < m; ++i) c[i] + = c[i-1]; +      for(i = n-1; I >= 0; i.) sa[--c[x[i]] = i; A      for(j = 1; J <= N; J <<= 1) { atp = 0; -          for(i = n-j; i < n; ++i) y[p++] = i; -          for(i = 0; i < n; ++i)if(Sa[i] >= j) y[p++] = sa[i]-J; -          for(i = 0; i < m; ++i) c[i] = 0; -          for(i = 0; i < n; ++i) c[x[y[i]]]++; -  in          for(i = 1; i < m; ++i) c[i] + = c[i-1]; -          for(i = n-1; I >= 0; i.) sa[--c[x[y[i]] [= Y[i]; to  +Swap (x, y); -p = 1; X[sa] = 0; the          for(i = 1; i < n; ++i) { *X[sa[i]] = cmp (y, sa[i-1], Sa[i], j)? P-1: p++; \$ Panax Notoginseng  -} the  +         if(P >= N) Break; AM= p; the  +  -} \$  \$     intk = 0; -n--; -      for(i = 0; I <= N; ++i) Rank[sa[i]] = i; the      for(i = 0; i < n; ++i) { -         if(k)--k;Wuyij = Sa[rank[i]-1]; the          while(Str[i+k] = = Str[j+k]) ++k; -Lcp[rank[i]] = k; Wu} -} About  \$ intLCP[MAXN], A[MAXN], SA[MAXN], RANK[MAXN]; -  - CharS[MAXN]; -  A intD[MAXN]; + intLen the  - voidRmq_init (intAintN) { \$      for(inti = 0; I < n; ++i) d[i] = A[i]; the      for(intj = 1; (1<<j) <= N; ++J) the          for(inti = 0; i + (1<<j)-1 < N; ++i) theD[i][j] = min (d[i][j-1], D[i + (1<< (j-1))][j-1]); the} -  in intASK (intLintR) { the     intk = 0; the      while((1<< (k+1)) <= r-l + 1) ++k; About     returnMin (D[l][k], d[r-(1<<k) + 1][k]); the} the  the intAskintLintR) { +     if(L = = r)returnLEN-SA[R];// L = = R is a string that returns its own length.  -     returnASK (l + 1, R);/// otherwise in RMQ query.  the}Bayi  the // the intMain () { -     intT -scanf ("%d", &t); the  the      while(t--) { the         intK thescanf ("%d", &k); -scanf ("%s", s); theLen = strlen (s); the          for(inti = 0; i < Len; ++i) { theA[i] = s[i]-' a ' + 1;94} theA[len] = 0; theDa (A, SA, Rank, LCP, Len, 30); theRmq_init (LCP, Len + 1);98         Long LongAns = 0; About          for(inti = 1; i + k-1 <= len; ++i) { -Ans + = Ask (I, i + k-1);101             if(i-1 > 0) ans-=-ask (i-1, i + k-1);/// pay attention to boundary problems. 102             if(i + k <= len) ans-=-ask (I, i + K);103             if(i-1 > 0 && i + k <= len) ans + = ask (I-1, i + K);104} theprintf ("%i64d\n", ans);106 107 108}109     return0; the}111 `

"Go" HDU 6194 string string (2017 Shenyang webcast-suffix array)

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