calculator

calculator

使用链表实现四则混合运算计算器（加减乘除和括号运算）：

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#include<stdio.h>
#include<stdlib.h>
struct Part{
    double  num;
    char  sign;
    struct Part *Pnext;
};

struct Part *create();
struct Part *transfer(struct Part *phead);
double caculate(struct Part *phead);

int main()
{
    struct Part *phead;
    phead=create();
    phead=transfer(phead);
    printf("\n%lf",caculate(phead));
    return 0;
}

struct Part *create()
{
    struct Part *phead=0,*ptemp=0,*ptail=0;
    double num;char sign;
    printf("****Welcome to magic caculator!****\n");
    printf("Input:");
    scanf("%lf%c",&num,&sign);
    while (1){  
    ptemp=(struct Part *)malloc(sizeof(struct Part));
    ptemp->num=num;
    ptemp->sign=sign;
    ptemp->Pnext=0;
    if (!phead)
    phead=ptail=ptemp;
    else {
        ptail->Pnext=ptemp;
        ptail=ptemp;
        }
    if (sign=='='||sign=='\n')
    break;
    scanf("%lf%c",&num,&sign);
    }
    return phead;
}

struct Part *transfer(struct Part *phead)
{
    struct Part *phead1;struct Part *p;
    phead1=phead;
    if (phead->sign=='*'){
        (phead->Pnext)->num=phead->num*(phead->Pnext)->num;
        phead->num=0;
        phead->sign='+';}
    if (phead->sign=='/'){
        (phead->Pnext)->num=phead->num/(phead->Pnext)->num;
        phead->num=0;
        phead->sign='+';}
    p=phead;
    phead=phead->Pnext;
    while (phead->sign!='='&&phead->sign!='\n'){
    if (phead->sign=='*'){
        (phead->Pnext)->num=phead->num*(phead->Pnext)->num;
        phead->num=0;
        if (p->sign=='+')
        phead->sign='+';
        else phead->sign='-';
    }

     if (phead->sign=='/'){
        (phead->Pnext)->num=phead->num/(phead->Pnext)->num;
        phead->num=0;
        if (p->sign=='+')
        phead->sign='+';
        else phead->sign='-';
    }
    p=phead;
    phead=phead->Pnext;
    }
    return phead1;
}

double caculate(struct Part *phead)
{
    double sum=phead->num;
    while (phead->sign!='\n'&&phead->sign!='='){
    if(phead->sign=='-')
    sum=sum-(phead->Pnext)->num;
    if(phead->sign=='+')
    sum=sum+(phead->Pnext)->num;
    phead=phead->Pnext;
    }
    return sum;
}