Exponentiation

Problems involving the computation of exact values of very large magnitude and precision are common. For example, the computation of the national debt is a taxing experience for many computer systems.

This problem requires that you write a program to compute the exact value of Rⁿ where R is a real number (0.0 < R < 99.999) and n is an integer such that .

Input 

Output 

Sample Input 

95.123 12
0.4321 20
5.1234 15
6.7592  9
98.999 10
1.0100 12

Sample Output 

548815620517731830194541.899025343415715973535967221869852721
.00000005148554641076956121994511276767154838481760200726351203835429763013462401
43992025569.928573701266488041146654993318703707511666295476720493953024
29448126.764121021618164430206909037173276672
90429072743629540498.107596019456651774561044010001
1.126825030131969720661201

#include<iostream>
#include<sstream>
#include<cstdio>
#include<string>
#include<cstring>
using namespace std;

#define MAX 1000000
int ans[MAX];

string Multi(string str1, string str2){
	int i;
	stringstream s;
	string str;

	memset(ans, 0, sizeof(ans));
	for(i = str1.size()-1; i >= 0; i--){
		for(int j = str2.size()-1, p = str1.size()-1-i; j >=0; j--, p++){
			ans[p] += (str1[i]-‘0‘)*(str2[j]-‘0‘);
		}
	}

	for(i = 0; i < MAX; i++){
		ans[i+1] += ans[i]/10;
		ans[i] = ans[i]%10;
	}

	for(i = MAX-1; i >=0; i--){
		if(ans[i])
			break;
	}
	if(i == -1)
		return "0";
	else{
		for(int j = i; j >= 0; j--){
			s << ans[j];
		}
		s >> str;
		return str;
	}	
}

int main(void){
	string str, ans;
	int n;

#ifndef ONLINE_JUDGE
	freopen("f:\\infile.txt", "r", stdin);
#endif

	while(cin >> str >> n){
		int dot, ansdot, i;
		ans = "1";
		dot = str.find(‘.‘, 0);
		ansdot = (str.size()-1-dot)*n;
		str.erase(dot, 1);
		for(i = 0; i < n; i++){
			ans = Multi(ans, str);
		}
		if(ans == "0"){
			cout << ".0" << endl;
			continue;
		}
		else{
			if(ans.size() < ansdot)
				ans.insert(0, ansdot-ans.size(), ‘0‘);
			ans.insert(ans.size()-ansdot, 1, ‘.‘);
		}
		for(i = ans.size()-1; i >=0; i--){
			if(ans[i] != ‘0‘)
				break;
		}
		ans.erase(ans.begin()+i+1, ans.end());
		cout << ans << endl;
	}
	return 0;
}

uva748 - Exponentiation,布布扣,bubuko.com

uva748 - Exponentiation

原文：http://blog.csdn.net/u011863942/article/details/25001949