如何用C语言写一个栈计算器

Question

如何用C语言写一个栈计算器？要求能实现带小数带括号的四则运算，以及幂运算

Answer 1

下面是一个用C语言编写的栈计算器的示例代码，可以实现带小数、带括号的四则运算和幂运算：

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>

// 定义栈结构
typedef struct {
    double* stack;
    int top;
    int capacity;
} Stack;

// 初始化栈
void initStack(Stack* s, int capacity) {
    s->stack = (double*)malloc(capacity * sizeof(double));
    s->top = -1;
    s->capacity = capacity;
}

// 判断栈是否为空
int isEmpty(Stack* s) {
    return s->top == -1;
}

// 判断栈是否已满
int isFull(Stack* s) {
    return s->top == s->capacity - 1;
}

// 入栈操作
void push(Stack* s, double value) {
    if (isFull(s)) {
        printf("Stack is full.\n");
        return;
    }
    s->stack[++s->top] = value;
}

// 出栈操作
double pop(Stack* s) {
    if (isEmpty(s)) {
        printf("Stack is empty.\n");
        return 0;
    }
    return s->stack[s->top--];
}

// 获取栈顶元素
double top(Stack* s) {
    if (isEmpty(s)) {
        printf("Stack is empty.\n");
        return 0;
    }
    return s->stack[s->top];
}

// 判断运算符的优先级
int getPriority(char op) {
    if (op == '+' || op == '-')
        return 1;
    if (op == '*' || op == '/')
        return 2;
    if (op == '^')
        return 3;
    return 0;
}

// 执行计算
double calculate(double a, double b, char op) {
    switch (op) {
        case '+':
            return a + b;
        case '-':
            return a - b;
        case '*':
            return a * b;
        case '/':
            return a / b;
        case '^':
            return pow(a, b);
    }
    return 0;
}

// 栈计算器函数
double stackCalculator(char* expression) {
    Stack numStack;  // 数字栈
    Stack opStack;   // 运算符栈
    initStack(&numStack, 100);
    initStack(&opStack, 100);
    
    int i = 0;
    while (expression[i] != '\0') {
        if (isdigit(expression[i])) {
            double num = 0;
            while (isdigit(expression[i])) {
                num = num * 10 + (expression[i] - '0');
                i++;
            }
            if (expression[i] == '.') {
                i++;
                double decimal = 0.1;
                while (isdigit(expression[i])) {
                    num = num + (expression[i] - '0') * decimal;
                    decimal /= 10;
                    i++;
                }
            }
            push(&numStack, num);
        } else if (expression[i] == '(') {
            push(&opStack, expression[i]);
            i++;
        } else if (expression[i] == ')') {
            while (top(&opStack) != '(') {
                char op = pop(&opStack);
                double b = pop(&numStack);
                double a = pop(&numStack);
                double result = calculate(a, b, op);
                push(&numStack, result);
            }
            pop(&opStack);  // 弹出左括号
            i++;
        } else if (expression[i] == '+' || expression[i] == '-' || expression[i] == '*' ||
                   expression[i] == '/' || expression[i] == '^') {
            while (!isEmpty(&opStack) && getPriority(top(&opStack)) >= getPriority(expression[i])) {
                char op = pop(&opStack);
                double b = pop(&numStack);
                double a = pop(&numStack);
                double result = calculate(a, b, op);
                push(&numStack, result);
            }
            push(&opStack, expression[i]);
            i++;
        } else {
            i++;
        }
    }
    
    while (!isEmpty(&opStack)) {
        char op = pop(&opStack);
        double b = pop(&numStack);
        double a = pop(&numStack);
        double result = calculate(a, b, op);
        push(&numStack, result);
    }
    
    double finalResult = pop(&numStack);
    
    free(numStack.stack);
    free(opStack.stack);
    
    return finalResult;
}

int main() {
    char expression[100];
    printf("请输入表达式：");
    fgets(expression, sizeof(expression), stdin);
    
    double result = stackCalculator(expression);
    printf("计算结果：%lf\n", result);
    
    return 0;
}

上述代码中使用两个栈，一个用于存储数字，另一个用于存储运算符。通过遍历表达式字符串，将数字和运算符依次入栈，并进行相应的计算操作，最后得到最终的计算结果。请注意，代码中对于错误情况的处理比较简单，可以根据实际需求进行适当修改和完善。