中綴表達式求值C語言實現(支持+-*/^五種運算

中綴表達式求值

通過把“中綴轉後綴”和“後綴求值”兩個算法功能集成在一起（非簡單的順序調用），

實現對中綴表達式直接求值，新算法還是從左到右掃描中綴表達式，

但同時使用兩個棧，一個暫存操作符，一個暫存操作數，來進行求值。

(支持 + - * / ^ 五種運算）
輸入格式:

共1行，爲1個字符串，即一箇中綴表達式，

其中每個數字或符號間由一個空格隔開。

輸出格式：

共1行，爲一個整數，即求值的結果。

輸入樣例：

( 2 + 3 ) * 6 + 4 / 2

輸出樣例：

32

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <malloc.h>
#include <math.h>
#define maximum 100000

typedef struct
{
    float data[maximum];
    int top;
}number;

typedef struct
{
    char data[maximum];
    int top;
}sign;

void InitNumber(number *stack);
void GetTopNumber(number stack, float *e);
void PushNumber(number *stack, float e);
void PopNumber(number *stack, float *e);

void InitSign(sign *stack);
void GetTopSign(sign stack, char *e);
void PushSign(sign *stack, char e);
void PopSign(sign *stack, char *e);

void Calculate(number *stack, char e);

number Num;
sign sig;
char expression[maximum];
	
int main()
{
    gets(expression);
    int length;
    length=strlen(expression);
    int i;
    float en,n;
    char es;
    InitNumber(&Num);
    InitSign(&sig);
    for (i=0;i<length;i++)
    {
        if(expression[i]>='0'&&expression[i]<='9')
        {
            n=expression[i]-'0';
            while (expression[i+1]!='\0')
            {
                if (expression[i+1]>='0'&&expression[i+1]<='9')
                {
                    n=n*10+expression[i+1]-'0';
                    ++i;
                }
                else break;
            }
            PushNumber(&Num,n);
        }
        else if (expression[i]=='+'||expression[i]=='-'||expression[i]=='*'||expression[i]=='/'||expression[i]=='^'||expression[i]=='('||expression[i]==')')
        {
            switch (expression[i])
            {
            case '+':
                if(sig.data[sig.top-1]!='+'&&sig.data[sig.top-1]!='-'&&sig.data[sig.top-1]!='*'&&sig.data[sig.top-1]!='/'&&sig.data[sig.top-1]!='^')
                    PushSign(&sig,'+');
                else
                {
                    while (sig.top>0&&sig.data[sig.top-1]!='(')
                    {
                        PopSign(&sig,&es);
                        Calculate(&Num,es);
                    }
                    PushSign(&sig,'+');
                }
                break;
            case '-':
                if(sig.data[sig.top-1]!='+'&&sig.data[sig.top-1]!='-'&&sig.data[sig.top-1]!='*'&&sig.data[sig.top-1]!='/'&&sig.data[sig.top-1]!='^')
                    PushSign(&sig,'-');
                else
                {
                    while (sig.top>0&&sig.data[sig.top-1]!='(')
                    {
                        PopSign(&sig,&es);
                        Calculate(&Num,es);
                    }
                    PushSign(&sig,'-');
                }
                break;
            case '*':
                if(sig.data[sig.top-1]!='*'&&sig.data[sig.top-1]!='/'&&sig.data[sig.top-1]!='^')
                    PushSign(&sig,'*');
                else
                {
                    while (sig.top>0&&sig.data[sig.top-1]!='(')
                    {
                        PopSign(&sig,&es);
                        Calculate(&Num,es);
                    }
                    PushSign(&sig,'*');
                }
                break;
            case '/':
                if(sig.data[sig.top-1]!='*'&&sig.data[sig.top-1]!='/'&&sig.data[sig.top-1]!='^')
                    PushSign(&sig,'/');
                else
                {
                    while (sig.top>0&&sig.data[sig.top-1]!='(')
                    {
                        PopSign(&sig,&es);
                        Calculate(&Num,es);
                    }
                    PushSign(&sig,'/');
                }
                break;
            case '^':
                if(sig.data[sig.top-1]!='^')
                    PushSign(&sig,'^');
                else
                {
                    while (sig.top>0&&sig.data[sig.top-1]!='(')
                    {
                        PopSign(&sig,&es);
                        Calculate(&Num,es);
                    }
                    PushSign(&sig,'^');
                }
            case '(':
                PushSign(&sig,'(');
                break;
            case ')':
                while (sig.data[sig.top-1]!='(')
                {
                    PopSign(&sig,&es);
                    Calculate(&Num,es);
                }
                PopSign(&sig,&es);
            }
        }
    }
    while (sig.top>0)
    {
        PopSign(&sig,&es);
        Calculate(&Num,es);
    }
    GetTopNumber(Num,&en);
    printf("%.0f\n",en);
    return 0;
}

void InitNumber(number *stack)
{
    stack->top=0;
}

void GetTopNumber(number stack, float *e)
{
    if(stack.top==0) return;
    else *e=stack.data[stack.top-1];
}

void PushNumber(number *stack, float e)
{
    if(stack->top>=maximum) return;
    else stack->data[stack->top++]=e;
}

void PopNumber(number *stack, float *e)
{
    if(stack->top==0) return;
    else *e=stack->data[--stack->top];
}

void InitSign(sign *stack)
{
    stack->top=0;
}

void GetTopSign(sign stack, char *e)
{
    if(stack.top==0) return;
    else *e=stack.data[stack.top-1];
}

void PushSign(sign *stack, char e)
{
    if(stack->top>=maximum) return;
    else 
	{
		stack->data[stack->top]=e;
		stack->top++;
	}
}

void PopSign(sign *stack, char *e)
{
    if(stack->top==0) return;
    else *e=stack->data[--stack->top];
}

void Calculate(number *stack, char e)
{
    float num1,num2,result;
    PopNumber(stack, &num2);
    PopNumber(stack, &num1);
    switch (e)
    {
        case '+':
            result=num1+num2;
            PushNumber(stack,result);
            break;
        case '-':
            result=num1-num2;
            PushNumber(stack,result);
            break;
        case '*':
            result=num1*num2;
            PushNumber(stack,result);
            break;
        case '/':
            if (num2==0) printf("表達式錯誤！");
            else
            {
                result=num1/num2;
                PushNumber(stack,result);
                break;
            }
        case '^':
            result=pow(num1,num2);
            PushNumber(stack,result);
            break;
    }
}