Description
A list is a sequence of zero or more elements, expressed in this form: [a1, a2, a3, ... , an], where each ai is one or more consecutive digits or lowercase letters. i.e. each list begins with a left square bracket, then zero or more elements separated by a single comma, followed by a right square bracket. There will be no whitespace characters (spaces, TABs etc) within a list.
In this problem, we use two list operations: append (++) and remove (--).
1. A ++ B: append elements in B to the end of A.
2. A -- B: remove all the elements in B, from A. If something appears more than once in B, remove it that many times in A. If there are many equal elements in A to choose from, remove them from left to right (until all occurrences are removed, or there is no need to remove more elements).
Your task is to write a calculator, evaluating simple expressions or the form "list1 ++ list2" or "list1 -- list2".
Input
There will be at most 10 expressions, one in each line, each having the form "list1 ++ list2" or "list1 -- list2", with no more than 80 characters in total (not counting the newline character). There will be exactly two spaces in each line: one before and one after the operator. Input ends with a single dot. The input is guaranteed to satisfy the restrictions stated above.
Output
For each expression, print its result on a single line.
Sample Input
[1,2,3] ++ [1,2,3] [a,b,c,t,d,e,t,x,y,t] -- [t] [a,b,c,t,d,e,t,x,y,t] -- [t,t,t,t] [123] ++ [456] .
Sample Output
[1,2,3,1,2,3] [a,b,c,d,e,t,x,y,t] [a,b,c,d,e,x,y] [123,456]
水题，字符串的处理，容易出错！
#include <iostream>
#include <stdio.h>
#include <string>
#include<list>
using namespace std;
int main()
{
list<string > q1,q2;
list<string>::iterator ptr1,ptr2;
char c;
string str;
int flag,temp,j;
while(scanf("%c",&c)!=EOF)
{
if(c=='.')
break;
q1.clear();
q2.clear();
while((c=getchar())!=EOF)
{
if(c==']')
break;
str="";
str+=c;
while((c=getchar())!=',')
{
if(c==']')
break;
str+=c;
}
q1.push_back(str);
if(c==']')
break;
}
getchar();
if((c=getchar())=='+')
flag=1;
else
flag=0;
getchar();
getchar();
getchar();
while((c=getchar())!=EOF)
{
if(c==']')
break;
str="";
str+=c;
while((c=getchar())!=',')
{ if(c==']')
break;
str+=c;
}
q2.push_back(str);
if(c==']')
break;
}
getchar();
if(flag)
{
printf("[");
temp=0;
for(ptr1=q1.begin(),j=1;ptr1!=q1.end();ptr1++,j++)
{
if(j!=q1.size())
{
cout<<*ptr1<<",";
temp=1;
}
else
{
cout<<*ptr1;
temp=1;
}
}
for(ptr1=q2.begin(),j=1;ptr1!=q2.end();ptr1++,j++)
{
cout<<","<<*ptr1;//这里要特别注意，错了几次
}
printf("]\n");
}
else
{
for(ptr1=q2.begin();ptr1!=q2.end();ptr1++)
{
for(ptr2=q1.begin();ptr2!=q1.end();ptr2++)
{
if(*ptr1==*ptr2)
{
*ptr2="A";
break;
}
}
}
temp=0;
for(ptr2=q1.end(),ptr2--,j=q1.size();j>=0;ptr2--,j--)
{
if(*ptr2!="A")
{
temp=j;
break;
}
}
cout<<"[";
for(ptr1=q1.begin(),j=1;ptr1!=q1.end();ptr1++,j++)
{
if((*ptr1!="A")&&(j!=temp))
cout<<*ptr1<<",";
else if((*ptr1!="A"))
cout<<*ptr1;
}
printf("]\n");
}
}
return 0;
}
