郁闷的C小加（三）中缀转前后缀并计算

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模板：各种缀的转换以及计算

代码：

#include<cstdio>#include<cstring>#include<algorithm>#include<iostream>#include<string>#include<vector>#include<stack>#include<bitset>#include<cstdlib>#include<cmath>#include<set>#include<list>#include<deque>#include<map>#include<queue>using namespace std;typedef long long ll;const double PI = acos(-1.0);const double eps = 1e-6;const int INF = 1000000000;const int maxn = 1234;int T,n,m;int ranks[maxn];//优先级char pre[maxn];//存前缀表达式char suf[maxn];//存后缀表达式void init_suf(){    ranks['=']=-1;    ranks['(']=0;    ranks['+']=ranks['-']=1;    ranks['*']=ranks['/']=2;    ranks[')']=3;}void init_pre(){    ranks['=']=-1;    ranks['(']=1;    ranks['+']=ranks['-']=1;    ranks['*']=ranks['/']=2;    ranks[')']=1;}double cal(char ch,double x,double y){    if(ch=='+')        return x+y;    else if(ch=='-')        return x-y;    else if(ch=='*')        return x*y;    else        return x/y;}void change_pre(char a[])//中缀转前缀{    init_pre();    stack<char>st;    char b[maxn];    int j=0;    int  len=strlen(a);    b[j++]='=';    for(int i=len-2;i>=0;i--)    {        if(isdigit(a[i])||a[i]=='.')//小数情况            b[j++]=a[i];        else        {            b[j++]='#';//分割运算数            if(a[i]==')')                st.push(a[i]);            else if(a[i]=='(')            {                while(!st.empty()&&st.top()!=')')                {                    b[j++]=st.top();                    st.pop();                }                st.pop();            }            else            {                while(!st.empty()&&ranks[a[i]]<ranks[st.top()])//把优先级大于他的都出栈                {                    b[j++]=st.top();                    st.pop();                }                st.push(a[i]);            }        }    }    while(!st.empty())//最后清空栈    {        b[j++]=st.top();        st.pop();    }    b[j]='\0';    int k=0;    for(int i=j-1;i>=0;i--)        pre[k++]=b[i];    pre[k]='\0';}double calculate_pre()//前缀表达式表达式的计算{    stack<double>q;    int len=strlen(pre);    for(int i=len-2;i>=0;i--)    {        if(pre[i]==' '||pre[i]=='#')            continue;        else if(isdigit(pre[i]))        {            while(isdigit(pre[i])||pre[i]=='.')//小数处理                i--;            i++;            double t=atof(&pre[i]);//atof:将字串转换成浮点型数            q.push(t);        }        else        {            double a=q.top();            q.pop();            double b=q.top();            q.pop();            q.push(cal(pre[i],a,b));        }    }    return q.top();}void change_suf(char a[])//中缀转后缀{    init_suf();    stack<char>st;    int j=0;    int  len=strlen(a);    st.push('=');//现将=压进栈为了之后的运算符好比较优先级    for(int i=0;a[i]!='=';i++)    {        if(isdigit(a[i])||a[i]=='.')//小数情况            suf[j++]=a[i];        else        {            suf[j++]='#';//分割运算数            if(a[i]=='(')                st.push(a[i]);            else if(a[i]==')')            {                while(st.top()!='(')                {                    suf[j++]=st.top();                    st.pop();                }                st.pop();            }            else            {                while(ranks[a[i]]<=ranks[st.top()])//把优先级大于他的都出栈                {                    suf[j++]=st.top();                    st.pop();                }                st.push(a[i]);            }        }    }    while(!st.empty())//最后清空栈    {        suf[j++]=st.top();        st.pop();    }    suf[j]='\0';}double calculate_suf()//后缀表达式的计算{    char c[maxn];    int j=0;    stack<double>st;    for(int i=0;suf[i]!='=';i++)    {        if(isdigit(suf[i])||suf[i]=='.')            c[j++]=suf[i];        else        {            if(j!=0)            {                st.push(atof(c));//字符串转数字函数的运用                memset(c,'\0',sizeof(c));                j=0;            }            if(suf[i]!='#')            {                double n1,n2;                n1=st.top();                st.pop();                n2=st.top();                st.pop();                st.push(cal(suf[i],n2,n1));//运算并入栈            }        }    }    return st.top();}void print(char pr[])//输出{    int i=0;    while(pr[i]=='#')            i++;    printf("%c",pr[i++]);    for(i=i;pr[i];i++)    {        if(pr[i]=='.'||(isdigit(pr[i])&&(isdigit(pr[i-1])||pr[i-1]=='.')))            printf("%c",pr[i]);        else if(pr[i]!='#')            printf(" %c",pr[i]);    }    printf("\n");}int main(){    scanf("%d",&T);    char a[maxn];    while(T--)    {        scanf("%s",a);        change_pre(a);        change_suf(a);        print(pre);        print(suf);        //printf("%.2f\n",calculate_suf());        printf("%.2f\n",calculate_pre());    }    return 0;}
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