C/C++ 编程计算2的100万次方（m的n次方）,超长结果输出文件

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <string>
#include <math.h>
#include <vector>
#include <sstream>
#include <list>
#include <algorithm>
#include <time.h>
#include <stdarg.h>

#include "myLibrary.h"
//头文件引用的较多,有一些和本程序无关

using namespace std;

const int M = 1000000;

int main(int argc, char *argv[])
{
	int arr[M];//每100万进一位,每位最大999999
	arr[0] = 1;
	int k, m, n, r, num = 1;//k保存单次计算乘积, m为底数(输入), n为幂数(输入), r进位, num为数组长度

	cout << "请输入要计算的内容以空格分隔,例m n(计算m的n次幂)：" << endl;
	while(1)
	{
		cin >> m >> n;
		if(!cin.fail() && m > 0 && n > 0)
			break;

		cin.clear();  // 错误位重置
                cin.sync();   // 清空缓存区 假设不加这个函数就死循环了
		cout << "输入错误,请又一次输入：" << endl;
	}

	//计算
	for(int i = 0; i < n; i++)
	{
		r = 0;
		for(int j = 0; j < num; j++)
		{
			k = arr[j] * m + r;
			arr[j] = k % M;
			r = k / M;
		}

		while(r > 0)
		{
			arr[num++] = r % M;
			r = r / M;
		}
	}

	//写文件
	FILE *fp = fopen("D:\\resoult.txt", "w");
	fprintf(fp, "计算%d的%d次幂\n", m, n);

	for(int i = num - 1; i >= 0; i--)
	{
		if(arr[i] < 100000 && arr[i] > 10000 && i != num -1)
			fprintf(fp, "%s", "0");
		else if(arr[i] < 10000 && arr[i] > 1000 && i != num -1)
			fprintf(fp, "%s", "00");
		else if(arr[i] < 1000 && arr[i] > 100 && i != num -1)
			fprintf(fp, "%s", "000");
		else if(arr[i] < 100 && arr[i] > 10 && i != num -1)
			fprintf(fp, "%s", "0000");
		else if(arr[i] < 10 && i != num -1)
			fprintf(fp, "%s", "00000");

		fprintf(fp, "%d", arr[i]);
	}
	fclose(fp);

	system("pause");
	return 0;
}