数据结构实验三不会的

1、二叉树表达式求值

基于二叉树的表达式求值

 

描述

 

输入一个表达式（表达式中的数均为小于10的正整数），利用二叉树来表示该表达式，创建表达式树，然后利用二叉树的遍历操作求表达式的值。

 

输入

多组数据。每组数据一行，为一个表达式，表达式以‘=’结尾。当输入只有一个“=”时，输入结束。

输出

每组数据输出一行，为表达式的值。

输入样例 1 

2*(2+5)=
1+2=
=

输出样例 1

14
3

#include<iostream>
#include<stack>
#include<string>
#include<cstring>
#include<queue>
using namespace std;
typedef struct Node* BinTree;
typedef BinTree BT;
string s;
queue<char> num;
queue<char> op;
struct Node 
{
    char Data;
    BT Left;
    BT Right;
    int ans;
};

int fact(char c)
{
    if (c >= '0' && c <= '9') return 1;
    else return 2;
}
BT createNode(char c)
{
    BT p = new Node;
    p->Data = c;
    p->Left = p->Right = NULL;
    if (fact(c) == 1)
        p->ans = c - '0';
    else
        p->ans = 0;
    return p;
}
BT createTree()
{
    for (int i = 0; i < s.size() - 1; i++) 
    {
        if (fact(s[i]) == 1)
            num.push(s[i]);
        else 
            op.push(s[i]);
    }
    BT Head = NULL;
    int flag = 0;     //标记有括号时的情况 
    int sflag = 0;      //处理开始时为括号的情况 
    if (s[0] == '(') sflag = 1;
    while (!op.empty())//非空
    {
        char option;
        option = op.front();//取第一个运算符
        op.pop();
        if (option != '(' && option != ')') 
        {
            BT T = createNode(option);
            if (option == '+' || option == '-')
            {
                if (flag == 0)
                {
                    if (Head == NULL)
                    {
                        T->Left = createNode(num.front());
                        num.pop();
                        T->Right = createNode(num.front());
                        num.pop();//取两个数，作为两个孩子
                    }
                    else
                    {
                        T->Left = Head;
                        T->Right = createNode(num.front());
                        num.pop();
                    }
                    Head = T;
                }
                else 
                {
                    if (Head == NULL)
                    {
                        T->Left = createNode(num.front());
                        num.pop();
                        T->Right = createNode(num.front());
                        num.pop();
                        Head = T;
                    }
                    else
                    {
                        T->Left = Head->Right;
                        Head->Right = T;
                        T->Right = createNode(num.front());
                        num.pop();
                    }
                }
            }
            else 
                if (option == '*' || option == '/')
                {
                if (flag == 0) 
                {
                    if (Head == NULL)
                    {
                        T->Left = createNode(num.front());
                        num.pop();
                        T->Right = createNode(num.front());
                        num.pop();
                        Head = T;
                    }
                    else 
                    {
                        if (sflag == 1 || Head->Data == '*' || Head->Data == '/')
                        {
                            T->Left = Head;
                            Head = T;
                            T->Right = createNode(num.front());
                            num.pop();
                            sflag = 0;
                        }
                        else
                        {
                            T->Left = Head->Right;
                            Head->Right = T;
                            T->Right = createNode(num.front());
                            num.pop();
                        }
                    }
                }
                if (flag == 1) 
                {
                    if (Head == NULL) 
                    {
                        T->Left = createNode(num.front());
                        num.pop();
                        T->Right = createNode(num.front());
                        num.pop();
                        Head = T;
                    }
                    else
                    {
                        T->Left = Head->Right;
                        Head->Right = T;
                        T->Right = createNode(num.front());
                        num.pop();
                    }
                }

            }
        }
        else if (option == '(')
        {
            flag = 1;
            
        }
        else if (option == ')')
        {
            flag = 0;
        }
    }
    return Head;
}

void solve(BT L) 
{
    if (L) 
    {
        solve(L->Left);
        solve(L->Right);
        char option = L->Data;
        if (option == '+') L->ans = L->Left->ans + L->Right->ans;
        if (option == '-') L->ans = L->Left->ans - L->Right->ans;
        if (option == '*') L->ans = L->Left->ans * L->Right->ans;
        if (option == '/') L->ans = L->Left->ans / L->Right->ans;

    }
}

int main() {
    while (cin >> s && s[0] != '=') 
    {
        BT H = createTree();
        solve(H);
        cout << H->ans << endl;
    }
    return 0;
}