PAT (Advanced Level) Practice 1060 Are They Equal

这题可以分两部，先求出要保留的数字部分，再求出指数部分，另外浮点数作为字符串处理时，一定要考虑前导0和末尾0，例如：000.00，0099.800。

给出一组比较容易错的数据：4 0000 0000.00 // YES 0.0000*10^0

#include <iostream>
#include <stdio.h>
#include <string>
using namespace std;
string chop(string str, int n){//获取有效数据
    string result = str;
    int index = result.find(".");
    if(index != string::npos){
       result.erase(index,1);
    }
    while(result.length()>1 && result[0]=='0'){
        result.erase(0,1);
    }
     while(result.length() > n){
            result.erase(result.length()-1,1);
        }
        while(result.length() < n){
            result += "0";
        }
        return result;
}

int getP(string str){//获取指数
    string result = str;
    while(result.length()>2 && result[0]=='0' && result[1]!='.'){
        result.erase(0,1);
    }
    int index = result.find(".");
    if(index ==string::npos){
        if(result[0]=='0'){ 
            return 0;
        }else{
            return result.length();
        }
    }else{
        if(result[0]=='0'){
            int m = 0;
            while(index+1<result.length() && result[index+1]=='0'){
                m--;
                index++;
            }
            if(index+1>=result.length()){
                return 0;
            }else{ 
                return m;
            }
        }else{ 
            return index;
        }
    }
}

int main()
{
    int n,len_a,len_b;
    string a,b;
    cin>>n>>a>>b;
    len_a = a.length();
    len_b = b.length();
    int pa,pb;//计算a b是十的多少次方
    pa = getP(a);
    pb = getP(b);
    string ra=chop(a,n);
    string rb=chop(b,n);
    if(ra == rb && pa == pb){
        cout<<"YES"<<" "<<"0."<<ra<<"*10^"<<pa<<endl;
    }else{
        cout<<"NO"<<" "<<"0."<<ra<<"*10^"<<pa<<" "<<"0."<<rb<<"*10^"<<pb<<endl;
    }
    return 0;
}