【PTA Advanced】1060 Are They Equal（C++）

目录

题目

Input Specification:

Output Specification:

Sample Input 1:

Sample Output 1:

Sample Input 2:

Sample Output 2:

思路

C++ 知识点UP

代码

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题目

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 0.123×105 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 10100, 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

难度评级：⭐️⭐️

1. 先去小数点

比如123.456变成123456*10^3

2. 再整数保留n位（比如n为3时）

即123456*10^3变成123*10^3

3. 最后确定次方数

即123*10^3中123为格式化后的小数部分，次方数由3变为3+n=6，最终为0.123*10^6

C++ 知识点UP

1. vector判断是否相等

vector相等是指容器内值和顺序都一致

可以直接用vec1==vect2这种方式去判断

2. 指针类型变量所指地址改值（注意*优先级）

比如：指针类型变量power所指地址的值需要+1时，不可以直接*power++，而要对*power加括号，即(*power)++，因为*的优先级低于++的优先级

代码

#include <iostream>
#include <vector>
#include <cmath>using namespace std;int n;vector<char> formatFloat(string str,int* power) {vector<char> res;// 先去小数点（eg.将123.456变成123456*10^-3） bool isBegin=true;bool afterPot=false; (*power)=0;for(int i=0;i<str.size();i++) {// 舍弃掉开头连续的0 if(isBegin&&str[i]=='0') {// 小数点后的0在舍弃时，power要变小 if(afterPot) (*power)--;continue;}// 遇到小数点时 if(str[i]=='.') {afterPot=true;}else {// 遇到数字时res.push_back(str[i]);if(afterPot) (*power)--;isBegin=false;	}  }// 这个数就是0时 if(isBegin) {res.push_back('0');*power=0;} // 计算整数部分只保留n位时的情况（eg.123456*10^-3变成123*10^-3） int diff=res.size()-n;if(!isBegin) (*power)+=diff; for(int i=0;i<abs(diff);i++) {if(diff>0) res.pop_back();else if(diff<0) res.push_back('0');}// res记录小数部分，power记录题目要求的format形式中的次方数if(!isBegin) (*power)+=n; return res;
}void printFormat(vector<char> vec, int power) {cout<<" 0.";for(int i=0;i<n;i++) {cout<<vec[i];}cout<<"*10^"<<power;
}int main(int argc, char** argv) {string a,b;cin>>n>>a>>b;int powerA,powerB;vector<char> aFormat=formatFloat(a,&powerA);vector<char> bFormat=formatFloat(b,&powerB);// 判断a b是否相等if(powerA==powerB&&aFormat==bFormat) {cout<<"YES";printFormat(aFormat,powerA); }else {cout<<"NO";printFormat(aFormat,powerA); printFormat(bFormat,powerB); 	}return 0;
}