Merge branch 'master' into develop

Author: xtaci

Makefile

@@ -3,7 +3,7 @@ CC=gcc
 CPP=g++
 AR=ar
 RANLIB=ranlib
-CFLAGS= -g -Wall -Wno-unused-function
+CFLAGS= -g -Wall -Wno-unused-function -std=gnu++0x
 SRCDIR = ./src
 INCLUDEDIR = -I./include -I.
 DEPS = 
@@ -68,7 +68,8 @@ PROGRAMS = m_based_demo \
 bubble_sort_demo \
 selection_sort_demo\
 8queue_demo \
-palindrome_demo
+palindrome_demo\
+suffix_array_demo
 
 all: $(PROGRAMS)
 

README.md

@@ -55,7 +55,7 @@
  Red-black tree
  Interval tree
  Prefix Tree(Trie)
- *Suffix Tree(未实现)*
+ Suffix Tree
  B-Tree
 
  Hash by multiplication
@@ -96,4 +96,4 @@
  wycg1984: for K-Means
  xmuliang: for HeapSort, Kruskal MST
  wyh267: for base64, LRU, bubble sort, selection sort
- ZhangYou0122 : Push-Relabel algorithm
+ ZhangYou0122 : Push-Relabel algorithm, SuffixTree

include/suffix_array.h

@@ -0,0 +1,92 @@
+/*
+ * suffix array algorithm
+ *
+ * Features: suffix array can sort all the suffixs in time complexity O(n*log^2(n)), and use memory in O(n).
+ * And suffix array can get two suffixs' longest common prefix(lcp) in O(log(n)) complexity. 
+ * You can test it by running suffix_array_demo.cpp
+ * Want to get more detailed information about suffix array? Please google SUFF_AR_ENG.pdf
+ *
+ * author: nowerzt@gmail.com
+ */
+
+#ifndef _SUFFIX_ARRAY_H
+#define _SUFFIX_ARRAY_H
+
+#include <algorithm>
+#include <vector>
+#include <string>
+#include <math.h>
+
+using namespace std;
+
+namespace alg {
+class SuffixArray {
+private:
+vector<vector<int> > bucket;
+vector<int> suffix;
+int N, L, K;
+const string& str;
+void suffix_sort();
+void update_bucket();
+
+bool less_than(int a, int b) { 
+if(K==0) return str[a]<str[b];
+else {
+if(bucket[K-1][a]==bucket[K-1][b]) return bucket[K-1][a+L/2]<bucket[K-1][b+L/2];
+else return bucket[K-1][a]<bucket[K-1][b];
+}
+}
+
+bool equal(int a, int b) {
+return !less_than(a,b) && !less_than(b,a);
+}
+
+public:
+explicit SuffixArray(const string& s) : N(s.size()), L(0), K(0), str(s) { suffix_sort();}
+// return the sorted suffix
+int operator [] (int i) { return suffix[i];}
+// Given two suffixs of string, return the longest common prefix length
+int lcp_length(int x, int y);
+};
+
+void SuffixArray::suffix_sort() {
+// init suffix
+suffix.resize(N);
+for(int i=0;i<N;i++) suffix[i]=i;
+// init bucket
+bucket.resize(ceil(log2(N))+1);
+for(size_t k=0;k<bucket.size();k++) bucket[k].resize(N+N);
+
+for(L=1,K=0;(L>>1)<N;L<<=1,K++) {
+sort(suffix.begin(), suffix.end(), bind(&SuffixArray::less_than, *this, placeholders::_1, placeholders::_2));
+update_bucket();
+}
+}
+
+
+void SuffixArray::update_bucket() {
+int seq=0;
+bucket[K][suffix[0]]=0;
+for(int i=1;i<N;i++) {
+if(!equal(suffix[i],suffix[i-1])) seq++;
+bucket[K][suffix[i]]=seq;
+}
+fill(bucket[K].begin()+N, bucket[K].end(), -1);
+}
+
+int SuffixArray::lcp_length(int x, int y) {
+if(x==y) return N-x;
+int ret=0;
+for(int k=K-1;k>=0 && x<N && y<N;k--) {
+if(bucket[k][x]==bucket[k][y]) {
+x += (1<<k);
+y += (1<<k);
+ret += (1<<k);
+}
+}
+return ret;
+}
+}
+
+#endif
+

src/suffix_array_demo.cpp

@@ -0,0 +1,37 @@
+#include <iostream>
+#include <string>
+#include <math.h>
+
+#include "suffix_array.h"
+
+using namespace std;
+using namespace alg;
+
+void print(string::iterator b, string::iterator e) {
+for(auto it=b;it!=e;++it) cout<<*it;
+}
+
+int main()
+{
+string str;
+while(cin>>str) {
+SuffixArray sa(str);
+cout<<endl;
+cout<<"sorted suffixs are:"<<endl;
+for(size_t i=0;i<str.size();i++) {
+print(str.begin()+sa[i], str.end());
+cout<<endl;
+}
+cout<<endl;
+cout<<"The length of the longest common prefix of two suffixs ";
+int i=rand()%str.size();
+int j=rand()%str.size();
+print(str.begin()+i,str.end());
+cout<<" and ";
+print(str.begin()+j,str.end());
+cout<<" is ";
+cout<<sa.lcp_length(i,j)<<endl;
+cout<<endl;
+}
+return 0;
+}