算法第四版5-2Tries_Trees

#include
#include
#include
using namespace std;
#define alphabet_size 256
//C++嵌套类
//1.嵌套类的名字只在外围类可见。
//2.类的私有成员只有类的成员和友元可以访问，因此外围类不可以访问嵌套类的私有成员。嵌套类可以访问外围类的成员（通过对象、指针或者引用）。
//3.一个好的嵌套类设计：嵌套类应该设成私有。嵌套类的成员和方法可以设为 public 。
//4.嵌套类可以直接访问外围类的静态成员、类型名（ typedef ）、枚举值。
class trie {
	const  static int R = alphabet_size;
	class node {
	public:
		int val;
		node* next[R];
		node() {
			for (int i = 0; i < R; i++) next[i] = NULL;
			val = NULL;
		}
		node(int v) {
			val = v;
			for (int i = 0; i < R; i++) next[i] = NULL;
		}
	};
	node* root;
public:
	trie() {
		root = NULL;
	}
	void put(string s, int v) {
		root = put(root, s, v, 0);
	}
	node* put(node* x, string s, int v, int d) {
		if (x == NULL) x = new node();
		if (d == s.length()) {
			x->val = v;
			return x;
		}
		char temp = s.at(d);
		x->next[temp] = put(x->next[(int)temp], s, v, d + 1);
		return x;
	}
	int get(string s) {
		node* temp = get(root, s, 0);
		if (temp == NULL) {
			perror("Invalid");
			return NULL;
		}
		return temp->val;
	}
	node* get(node* x, string s, int d) {
		if (x == NULL) return NULL;
		if (d == s.length()) return x;
		char temp = s.at(d);
		return get(x->next[temp], s, d + 1);
	}
	queue keywithprefix(string pre) {   //find all keys that start from p
		queue res;     // use queue to record the key with prefix
		collect(get(root, pre, 0), pre, res);
		return res;
	}
	void collect(node* x, string p, queue &q) {
		if (x == NULL) return;
		//cout << p << endl;   //调试递归调用，加栈标识符
		if (x->val != NULL) {
			q.push(p);
		}
		for (int i = 0; i < R; i++) {  // char 为-128到128，有负值，不能作为index；改用unsigned char或者int，使用（char）转换为char
			/*if ((int)i == 111||(int)i==101||(int)i==255) {
				system("pause");
			}*/
			//cout << (int)i << endl;   // 调试循环，输出标识，记录进入函数时的i值
			collect(x->next[i], p + (char)i, q);   // check everyone but enqueue the certain ones
		}
	}
	queue keythatmatch(string pat) {   //find all keys that exactly match pat
		queue res;
		collect(root, "", pat, res);
		return res;
	}
	void collect(node* x, string p, string pat, queue &q) {   //use p to record the paths
		if (x == NULL) return;
		int d = p.length();   //use string length as the signal of end recurrence
		if (d == pat.length() && x->val != NULL) q.push(p);   //all match and the key is valid(x->val!=NULL)
		if (d == pat.length()) return;   //end match or not match
		for (int i = 0; i < R; i++) {
			if (pat.at(d) == '.' || i == pat.at(d)) {  //单引号为char，双引号为字符串（const char*），结尾有\0 ； string.at(d)为char类型单字符，不能和双引号比较
				collect(x->next[i], p + (char)i, pat, q);
			}
		}
	}
	string longestprefix(string s) {
		int len = search(root, s, 0, 0);
		return s.substr(0, len);
	}
	// d for the current seacrhing index,len save the length of the matched valid key,not index
	int search(node* x, string s, int d, int len) {
		if (x == NULL) return len;
		if (x->val != NULL) len = d;   //in the first recur,d=0,x=root,has 0 letter,so length is 0
								  //in the second recur,d=1,x=root->next[i],has one letter,if match,length=1
								  //in the last,eg,d=n,x=last_letter,has all string,so length=n
		if (d == s.length()) return len;
		return search(x->next[s.at(d)], s, d + 1, len);
		//in the last case,d=n-1,s.at[d] refer the last letter(valid),d+1=s.length(),if match,len=s.length() (valid) 
	}
	void del(string s) {
		root = del(root, s, 0);
	}
	//just set val=NULL,not delete the node ,unless all node->next=NULL
	node* del(node* x, string s, int d) {
		if (x == NULL) {
			perror("valid key");
			return root;
		}
		if (d == s.length()) x->val = NULL;
		else {
			x->next[s.at(d)] = del(x->next[s.at(d)], s, d + 1);
			//return the deleted node*,if NULL,set next[x] NULL,or update next[x]
			//assign to x->next[] to update itself,commonly used in recur_delete operation
		}
		// !!!
		if (x->val != NULL) return x;
		//avoid delete node with same prefix but has value,eg delete shell-1,avoid delete she-5
		//prevent delete the prefix has value but no other subtree,it's next array is all NULL excepet the delete one
		for (int i = 0; i < R; i++) {
			if (x->next[i] != NULL) return x;   //if all next[] is NULL,return NULL,to set pa's next[this]=NULL
		}
		return NULL;
	}
};
int main() {
	int a, n;
	string s;
	trie t;
	queue q;
	while (true) {
		cin >> n;
		while (n--) {
			cin >> s >> a;
			t.put(s, a);
		}
		cin >> s;
		cout << t.get(s) << endl;
		cin >> s;

		q = t.keywithprefix(s);
		while (!q.empty()) {
			cout << q.front() << endl;
			q.pop();
		}
		cin >> s;
		q = t.keythatmatch(s);
		while (!q.empty()) {
			cout << q.front() << endl;
			q.pop();
		}
		cin >> s;
		cout << t.longestprefix(s) << endl;
		cin >> s;
		t.del(s);
		cout << t.longestprefix(s) << endl;
	}
	return 0;
}

Algorithm 5-2