前缀转中缀（利用栈）

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#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <time.h>#include<stack>using namespace std;struct node{int type;string s;void kuo(){s="("+s+")";}node(int t,string str){type=t;s=str;}};stack<node> sta;char s[100];void push(int t,string s){if(t==1){while(!sta.empty() && sta.top().type==1){node node1=sta.top();sta.pop();node node2=sta.top();sta.pop();s="("+node1.s+node2.s+s+")";}sta.push(node(1,s));}else{sta.push(node(0,s));}}int main(){    freopen("in","r",stdin);    //freopen("out.txt","w",stdout);   while(gets(s)!=NULL){int len=strlen(s);while(!sta.empty()) sta.pop();for(int i=0;i<len;){if(s[i]>='0' && s[i]<='9' ){string tmp="";while(i<len && s[i]>='0' && s[i]<='9'){tmp+=s[i];i++;}push(1,tmp);}else if(s[i]>='a' && s[i]<='z' || s[i]>='A' && s[i]<='Z'){string tmp="";tmp+=s[i];push(1,tmp);i++;}else if(s[i]=='|' || s[i]=='&'         || s[i]=='>' && s[i+1]=='='        || s[i]=='<' && s[i+1]=='='        || s[i]=='=' && s[i+1]=='='        || s[i]=='!' && s[i+1]=='='        ){string tmp="";tmp+=s[i];tmp+=s[i+1];i+=2;push(0,tmp);}else{string tmp="";tmp+=s[i];push(0,tmp);i++;}}cout<<sta.top().s<<endl;}    return 0;}

input：
+-*+ABD/E+F*ADC

output：

((((A+B)*D)-(E/(F+(A*D))))+C)

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