Add prefix tree

Author: xtaci

Makefile

@@ -46,7 +46,8 @@ PROGRAMS = m_based \
 sha1_demo\
 huffman_demo \
 word_seg_demo \
-md5_demo
+md5_demo \
+trie_demo
 
 
 all: $(PROGRAMS)

include/trie.h

@@ -0,0 +1,127 @@
+/*******************************************************************************
+ * DANIEL'S ALGORITHM IMPLEMENTAIONS
+ *
+ * /\ | _ _ ._ o _|_ |_ ._ _ _ 
+ * /--\ | (_| (_) | | |_ | | | | | _> 
+ * _| 
+ *
+ * Trie (Prefix tree)
+ *
+ * http://en.wikipedia.org/wiki/Trie
+ ******************************************************************************/
+
+#ifndef __TRIE_H__
+#define __TRIE_H__
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+namespace alg {
+const int NUMWORD = 26;
+
+class Trie {
+private:
+class node {
+public:
+int words;
+int prefixes;
+node *edges[NUMWORD];
+node():words(0),prefixes(0) {
+memset(edges, 0, sizeof(edges));
+}
+~node() {
+for (int i=0;i<NUMWORD;i++) {
+if (edges[i] != NULL) {
+delete edges[i];
+}
+}
+}
+};
+node *m_root;
+public:
+Trie() {
+m_root = new node;
+}
+
+~Trie() {
+delete m_root;
+m_root=NULL;
+}
+
+void Add(char * str) {
+_lowercase(str);
+_add(m_root, str);
+}
+
+int Count(char *str) {
+char * _str = strdup(str);
+_lowercase(_str);
+
+int cnt = _count(m_root, _str);
+free(_str);
+return cnt;
+}
+
+int CountPrefix(char *prefix) {
+char * _str = strdup(prefix);
+_lowercase(_str);
+
+int cnt = _count_prefix(m_root, _str);
+free(_str);
+return cnt;
+}
+
+private:
+void _lowercase(char *str) 
+{
+int i;
+for (i=0;str[i];i++) {
+str[i] = tolower(str[i]);
+}
+}
+
+void _add(node *n, char * str) {
+if (str[0] == '\0') {
+n->words++;
+} else {
+n->prefixes++;
+int index=str[0]-'a';
+if (n->edges[index]==NULL) {
+n->edges[index] = new node;
+}
+
+_add(n->edges[index], ++str);
+} 
+}
+
+int _count(node *n, char * str) {
+if (str[0] == '\0') {
+return n->words;
+} else {
+int index=str[0]-'a';
+if (n->edges[index]==NULL) {
+return 0;
+}
+
+return _count(n->edges[index], ++str);
+} 
+}
+
+int _count_prefix(node *n, char * str) {
+if (str[0] == '\0') {
+return n->prefixes;
+} else {
+int index=str[0]-'a';
+if (n->edges[index]==NULL) {
+return 0;
+}
+
+return _count_prefix(n->edges[index], ++str);
+} 
+}
+};
+}
+
+#endif //

src/trie_demo.cpp

@@ -0,0 +1,15 @@
+#include "trie.h"
+
+int main(void) {
+alg::Trie trie;
+const char *strs[] = {"sap", "sat", "sad", "rat", "ram", "rag", "rap", "sat", "ram","rag", "nap", "Nat", "lap"};
+
+for (uint32_t i=0;i<sizeof(strs)/sizeof(char*);i++) {
+char * str = strdup(strs[i]);
+trie.Add(str);
+free(str);
+}
+
+printf("count of :%s %d\n", "sat", trie.Count("sat"));
+printf("count of prefix :%s %d\n", "ra", trie.CountPrefix("ra"));
+}