【PAT甲级】1060 Are They Equal (25)

题目链接

If a machine can save only 3 significant digits, the float numbers 12300 and 12358.9 are considered equal since they are both saved as 0.123*10^5^ with simple chopping. Now given the number of significant digits on a machine and two float numbers, you are supposed to tell if they are treated equal in that machine.

Input Specification:

Each input file contains one test case which gives three numbers N, A and B, where N (<100) is the number of significant digits, and A and B are the two float numbers to be compared. Each float number is non-negative, no greater than 10^100^, and that its total digit number is less than 100.

Output Specification:

For each test case, print in a line "YES" if the two numbers are treated equal, and then the number in the standard form "0.d~1~...d~N~*10\^k" (d~1~>0 unless the number is 0); or "NO" if they are not treated equal, and then the two numbers in their standard form. All the terms must be separated by a space, with no extra space at the end of a line.

Note: Simple chopping is assumed without rounding.

Sample Input 1:

3 12300 12358.9

Sample Output 1:

YES 0.123*10^5

Sample Input 2:

3 120 128

Sample Output 2:

NO 0.120*10^3 0.128*10^3

思路：

１、首先判断是否为小数，去掉前导０

２、找到小数点去掉，再计算小数点后有几位连续的０

３、保留ｎ位有效数字

４、比较有效数字和指数，　输出对应结果

代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <string>
#include <map>
#include <queue>
#include <stack>
#include <cmath>
#include <vector>
#include <sstream>
#include <algorithm>
using namespace std;
#define rep(i,a,n) for(int i=a;i<n;i++)
#define mem(a,n) memset(a,n,sizeof(a))
#define lowbit(i) ((i)&(-i))
typedef long long ll;
typedef unsigned long long ull;
const ll INF=0x3f3f3f3f;
const int N = 1e6+5;

int n;
string deal(string s,int& e) {
    int k=0;
    while(s.length()>0 && s[0]=='0'){			///去掉前导０
		s.erase(s.begin());
	}
    if(s[0]=='.') { ///第一位是小数点
        s.erase(s.begin());
        while(s.length()>0&&s[0]=='0') { ///小数点后面还有几个连续0
            s.erase(s.begin());
            e--;
        }
    } else {///小数点之前有几位非0数
        while(k<s.length()&&s[k]!='.') {
            k++,e++;
        }
        if(k<s.length()) s.erase(s.begin()+k);///去掉小数点
    }
//    cout<<e<<endl;
    if(s.length()==0) e=0;///str 对应的数值为0
    int num=0;
    k=0;
    string res("");
    while(num<n) {
        if(k<s.length()) res+=s[k++];
        else res+='0';
        num++;
    }
////    cout<<"e="<<e<<endl;
    return res;
}
int main() {
    string s1,s2,s3,s4;
    cin>>n>>s1>>s2;
    int e1=0,e2=0;
    s3 = deal(s1,e1);
    s4 = deal(s2,e2);
//    cout<<"s3 = "<<s3<<"  s4 = "<<s4<<endl;
    if(s3==s4&&e1==e2) {
        cout<<"YES 0."<<s3<<"*10^"<<e1;
    } else {
        cout<<"NO 0."<<s3<<"*10^"<<e1<<" 0."<<s4<<"*10^"<<e2;
    }
    return 0;
}