ZOJ 2476 Total Amount

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <vector>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <functional>
#include <string>
#include <map>
#include <cctype>

using namespace std;

char str[200];

int main()
{
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    int n;
    char ch;
    double num;
    double sum;
    while(scanf("%d",&n)!=EOF)
    {
        getchar();
        if(n==0)
            break;
        sum=0;
        for(int i=0; i<n; i++)
        {
            num=0;
            bool isxiaoshu=false;
            double xiaoshu=0.1;
            while(true)
            {
                ch=getchar();
                if(ch=='$'||ch==',')
                    continue;
                else if(ch=='.')
                {
                    isxiaoshu=true;
                }
                else if(ch=='\n')
                {
                    break;
                }
                else
                {
                    if(isxiaoshu)
                    {
                        num+=(ch-'0')*xiaoshu;
                        xiaoshu=xiaoshu/10;
                    }
                    else
                    {
                        num=num*10+ch-'0';
                    }
                }
            }
            sum+=num;
        }
        sprintf(str,"%.2lf",sum);

        int len=strlen(str);
        printf("$");
        int f=(len-3)%3;
        int c=(len-3)/3;
        int index=0;
        for(; index<f; index++)
        {
            printf("%c",str[index]);
        }
        for(int i=0; i<c; i++)
        {
            if(index!=0)
                printf(",");
            printf("%c",str[index++]);
            printf("%c",str[index++]);
            printf("%c",str[index++]);
        }
        printf("%c",str[index++]);
        printf("%c",str[index++]);
        printf("%c",str[index++]);
        printf("\n");
    }
    return 0 ;
}