数据结构实验3——用栈求解算术表达式

算数表达式中出现的数都在10以内

代码如下

#include <iostream>
#include <cstdio>
#include <cwchar>
#include <windows.h>

using namespace std;
#define ok 1
#define error 0
#define overflow -2
#define maxn 100

typedef struct{
    char *base;
    char *top;
    int stacksize;
}SqStack;

typedef struct SNode{
    int data;
    struct SNode *next;
}SNode, *linkstack;

char ch, theta, x;
SqStack OPTR, OPND;
char oper[7] = {'(', ')', '+', '-', '*', '/','#'};
//栈的初始化
int initStack(SqStack &s){
    s.base = new char[maxn];
    if(!s.base) exit(overflow);
    s.top = s.base;
    s.stacksize = maxn;
    return ok;
}

//入栈
int push(SqStack &s, char e){
    if(s.base - s.top == s.stacksize) return error;
    *s.top ++ = e;
    return ok;
}

//出栈
int pop(SqStack &s, char &e){
    if(s.base == s.top) return error;
    e = *--s.top;
    return ok;
}

char gettop(SqStack s){
    if(s.top != s.base)
        return *(s.top - 1);
}

//判断栈是否为空
bool stackempty(SqStack &s){
    return s.top != s.base;
}

bool in(char ch){
    for(int i = 0; i < 7; i ++ )
        if(ch == oper[i]) return true;
    return false;
}

char precede(char theta1, char theta2){
    if((theta1 == '(' && theta2 == ')') || (theta1 == '#' && theta2 == '#'))
        return '=';
    else if (theta1 == '(' || theta1 =='#' || theta2== '(' || ((theta1=='+'||theta1=='-') && (theta2 == '*'||theta2 =='/')))
        return '<';
    else return '>';
}

char operate(char first, char theta, char second){
    switch(theta){
        case '+': return (first - '0') + (second - '0') + 48;
        case '-': return (first - '0') - (second - '0') + 48;
        case '*': return (first - '0') * (second - '0') + 48;
        case '/': return (first - '0') / (second - '0') + 48;
    }
    return 0;
}

char evaluateExpression(){
    int j = initStack(OPND);
    j = initStack(OPTR);
    j = push(OPTR, '#');
    cin >> ch;
    while(ch != '#' || gettop(OPTR) != '#'){
        char a, b;
        if(!in(ch)) {
            j = push(OPND, ch);
            cin >> ch;
        }
        else {
            switch (precede(gettop(OPTR), ch)) {
                case '<': {
                    j = push(OPTR, ch);
                    cin >> ch;
                    break;
                }
                case '>': {
                    j = pop(OPTR, theta);
                    j = pop(OPND, b);
                    j = pop(OPND, a);
                    j = push(OPND, operate(a, theta, b));
                    break;
                }
                case '=': {
                    j = pop(OPTR, x);
                    cin >> ch;
                    break;
                }
            }
        }
    }
    return gettop(OPND);
}

int main()
{
    char res;
    int c;
    SetConsoleOutputCP(65001);
    cout<<"-----------------"<<endl;
    cout<<"0-9之内的多项式计算"<<endl;
    cout<<"1.计算"<<endl;
    cout<<"0.退出"<<endl;
    cout<<"请选择：";
    while(scanf("%d", &c) != EOF){
        switch(c){
            case 1:{
                cout<<"请输入要计算的表达式（操作数和结果都在0-9的范围内,以#结束）："<<endl;
                res = evaluateExpression();
                cout<<"计算结果为"<<res - 48<<endl<<endl;
                break;
            }
            case 0:{
                cout<<"退出成功
"<<endl;
                exit(0);
            }
            default:
                break;
        }
    }
}

 

clion下运行成功

总结：写这个中间隔了大概有十天，再打开的时候不记得写哪了，以后记得要多写注释，标注写到哪里了orz