广义表的c/c++描述（下），代码篇

  本程序改编自课本例题，包括广义链表的建立，输出，求链表长度，深度，求原子个数和最大原子（ascii）。大量应用了递归。全部代码如下：（感觉学习递归也没啥太好的方法，对问题情景理解透彻后，自然就会确定递归体了，做到对问题分析的不重不漏）

#include<iostream>
using namespace std;
#include<stdio.h>
struct Node {
	int type;   //1 表示子表表头  0表示原子节点
	union {
		char value;
		Node* ptChildHead;
	}valOrPt;
	Node* ptNext;
};
Node* creatGenerList(char *&ptCHar) {
	Node* pt;
	char s = *ptCHar;    //简单的标准例子如(a,b,c,d)
	if (s == '(') {
		pt = new Node;

		pt->type = 1;  //1 is child list, 0 is value
		ptCHar++;
		pt->valOrPt.ptChildHead = creatGenerList(ptCHar);//深度递归，建立子表
	}
	else if (s == '#') {
		ptCHar++;//通过与后面的ptChar++结合，使字符指针越过右括号，在后面的
		return NULL;//if判断里，判断的是右括号后的逗号或'\0'
	}
	else if (s == '\0')//当给了空字符串，表示表不存在，连空表都不算
		pt = NULL;
	else {    //表明传递来的是字符，建立原子节点
		pt = new Node;
		pt->type = 0;
		pt->valOrPt.value = s;
	}

	ptCHar++;
	s = *ptCHar;

	if(pt != NULL)  //当这个表存在时，可以为空表，这是为了程序的健壮性
		if (s == ',') {
			ptCHar++;
			pt->ptNext = creatGenerList(ptCHar);//广度递归,建立同层下一个元素节点
		}
		else if (s == ')' || s == '\0')//与'\0'比较，是为了区分(#)与((#),a)与(a,(#))
			pt->ptNext = NULL;
	
	return pt;
//通过这四个例子模拟加想象，递归过程已可以保证是正确的。
}

void displayList(Node* ptHead) {
	if (ptHead == NULL) return;//对应于表不存在，连空表都不是
	
	if (ptHead->type == 0) 
		cout << ptHead->valOrPt.value;
	else if (ptHead->type == 1) {
		cout << '(';
		if (ptHead->valOrPt.ptChildHead == NULL)
			cout << "#";
		else
			displayList(ptHead->valOrPt.ptChildHead);

		cout << ')';//这个右括号加的是神来之笔，把表作为元素看待
	}

	if (ptHead->ptNext != NULL) {
		cout << ',';
		displayList(ptHead->ptNext);
	}
}
int lengthList(Node* ptHead) {
	if (ptHead == NULL) return 0; //表不存在
	
	int length = 0;
	ptHead = ptHead->valOrPt.ptChildHead;
	while(ptHead != NULL) {
		length++;
		ptHead = ptHead->ptNext;
	}
	return length;  //表不存在或者为空表，都返回0
}
int depthList(Node *ptHead) { 
	if (ptHead->type == 0)
		return 0;
	else if (ptHead->valOrPt.ptChildHead == NULL)
		return 1;
	else {
		int max = 0;
		ptHead = ptHead->valOrPt.ptChildHead;
		while (ptHead != NULL) {
			if (max < depthList(ptHead))
				max = depthList(ptHead);
			ptHead = ptHead->ptNext;
		}

		return max + 1;
	}

}
int numberOfAtomic(Node *ptHead) { 
	//表不存在,或者是遇到了空表
	if (ptHead == NULL || ptHead->valOrPt.ptChildHead == NULL) 
		return 0;
	
	ptHead = ptHead->valOrPt.ptChildHead;
	int number = 0;
	while (ptHead != NULL) {
		if (ptHead->type == 0)
			number++;
		else
			number += numberOfAtomic(ptHead);
		ptHead = ptHead->ptNext;
	}

	return number;

}

char bigggestChar(Node *ptHead) {
	if (ptHead == NULL || ptHead->valOrPt.ptChildHead == NULL)
		return '\0';

	char s = '\0';
	ptHead = ptHead->valOrPt.ptChildHead;
	while (ptHead != NULL) {
		if (ptHead->type == 0 && s < ptHead->valOrPt.value)
			s = ptHead->valOrPt.value;
		else if (ptHead->type == 1 && s < bigggestChar(ptHead))
			s = bigggestChar(ptHead);
		ptHead = ptHead->ptNext;
	}

	return s;
}
int main() {
	char chars[100] = "(b,(b,a,(#),d),((a,m),c,((#))))";
	char* ptChar = chars;
	Node* ptHead = creatGenerList(ptChar);

	cout << "the list is as follows : ";
	displayList(ptHead);
	
	cout << endl << "list length is : " << lengthList(ptHead);
	cout << endl << "list depth is : " << depthList(ptHead);
	cout << endl << "numbers of atomic elements is :" << numberOfAtomic(ptHead);
	cout << endl << "the biggest char is : " << bigggestChar(ptHead);

	return 0;
}

  测试结果如下：

  换多个字符串例子，测试结果都可以准确显示。谢谢阅读。看代码，建议复制到vs studio里，条理层次关系会更清晰。