求任意数的任意次方（C++）

Source Code

Problem: 1001

Memory: 244K
Time: 47MS

Language: C++
Result: Accepted

• Source Code

  #include <iostream>
  #include <string>
  #include <algorithm>
  using namespace std;
  
  string multiWithChar(string a,char b);
  string multiWithString(string a,string b);
  string addWithString(string a,string b);
  int getPointNum(string a,int r);
  string deletePoint(string);
  string deleteInsignificant(string);
  string Exponentiation(string,int);
  string recoverPoint(string,int);
  string solve(string,int);
  
  int main()
  {
  	string s;
  	int n;
  
  	while(cin>>s>>n)
  	{
  		cout<<solve(s,n)<<endl;
  		
  	}
  	return 0;
  }
  string solve(string a, int r)
  {
  
  	int pointnum=getPointNum(a,r);
  	return deleteInsignificant(recoverPoint(Exponentiation(deletePoint(a),r),pointnum));
  }
  string multiWithChar(string a,char b_)
  {
  	int len=a.length();
  	int up=0;
  	int b=b_-'0';
  	string ret="";
  	for (int i=len-1;i>=0;i--)
  	{
  		int w=(a.at(i)-'0')*b;	
  		ret.append(1,(up+w)%10+'0');
  		up=(w+up)/10;	
  	}
  	if(up!=0)
  	ret.append(1,up+'0');
  	std::reverse(ret.begin(),ret.end());
  	return ret;
  }
  string multiWithString(string a,string b)
  {
  	
  	string ret="";
  	int appnum=0;
  	for (int i=b.length()-1;i>=0;i--)
  	{
  		string temp=multiWithChar(a,b.at(i));
  		temp.append(appnum++,'0');
  		ret=addWithString(ret,temp);
  
  	}
  	return ret;
  }
  string addWithString(string a,string b)
  {
  
  	if(a=="")return b;
  	if(b=="")return a;
  	string temp;
  	if(a.length()<b.length()){
  		temp=a;
  		a=b;
  		b=temp;
  	}
  	int maxlen=a.length();
  	int minlen=b.length();
  	int up=0;
  	string ret="";
  	for (int i=maxlen-1,j=minlen-1;i>=0;i--,j--)
  	{
  	
  		int w=((j<0)?0:(b.at(j)-'0'))+(a.at(i)-'0');
  		ret.append(1,(up+w)%10+'0');
  		up=(w+up)/10;
  	}
  	
  	if(up!=0)
  	ret.append(1,up+'0');
  	std::reverse(ret.begin(),ret.end());
  	return ret;
  }
  int getPointNum(string a,int r)
  {
  	int pos=a.find('.');
  	if(pos==-1)return 0;
  	return (a.length()-1-pos)*r;
  
  }
  string deletePoint(string s)
  {
  	int pos=s.find('.');
  	if(-1==pos)return s;
  	return s.substr(0,pos).append(s.substr(pos+1));
  }
  string deleteInsignificant(string s)
  {
  	if(s.find('.')==-1)return s;
  	int i=s.length();
  
  	while (s.at(i-1)=='0')
  	{
  		i--;
  
  	}
  	if(s.at(i-1)=='.')i--;
  	if(s.at(0)=='0')s=s.substr(1,i);
  	return s.substr(0,i);
  }
  string Exponentiation(string r,int n)
  {
  	string ret="";
  	if(n==1)return r;
  	if(n==2)
  	{
  		return multiWithString(r,r);
  	}
  	else if(n%2==0)
  	{
  		return Exponentiation(Exponentiation(r,2),n/2);
  	}
  	else 
  	{
  		return multiWithString(r,Exponentiation(r,n-1));
  	}
  
  	
  }
  string recoverPoint(string s,int pointnums)
  {
  	if(!pointnums)return s;
  	s=s.insert(s.length()-pointnums,".");
  	return s;
  }