把大数据结构体封装一下，然后重载操作符号，这样书写代码就清爽多了. 时间是0MS

#include <stdio.h>
#include <string.h>
#define MAXLEN 180
typedef struct st_bignumber
{
	int nLen ;
	int nData[MAXLEN] ;
	st_bignumber()
	{
		reset();
	} ;
	st_bignumber(const struct st_bignumber &other)
	{
		nLen = other.nLen ;
		memcpy(nData,other.nData,sizeof(nData[0])* nLen) ;
	} ;
	void reset()
	{
		nLen = 0 ;
		memset(nData,0,sizeof(nData)) ;
	}
	st_bignumber operator = ( const struct st_bignumber & other)
	{
		nLen = other.nLen ;
		memset(nData,0,sizeof(nData)) ;
		memcpy(nData,other.nData,sizeof(nData[0])* nLen) ;
		return * this ;
	}
	st_bignumber operator * ( const struct st_bignumber & other)
	{
		struct st_bignumber res ;
		int i ,j ;
		for ( i = 0 ;i < nLen ;i ++ )
		{
			for (j = 0 ;j < other.nLen; j ++ )
			{
				res.nData[i+j] += this->nData[i] * other.nData[j] ;
			}
		}

		for( i = 0 ;i < nLen + other.nLen ;i ++)
		{
			if( res.nData[i] >= 10)
			{
				res.nData[i+1] += ( res.nData[i] / 10) ;
				res.nData[i] %= 10 ;
			}
			if( res.nData[i] != 0)
				res.nLen = i + 1 ;
		}
		return res ;
	}

}bignumber;


int main( void )
{
	char s[10];
	int n , i ;
	int nRealCount ;
	bignumber number,result, tmp;
	while(scanf("%s%d",s,&n)==2)
	{
		nRealCount = 0 ;
		number.reset() ;
		for( i = strlen(s) -1 ;i >= 0 ;i -- )
		{
			if( s[i] =='0')
				s[i] = '\0' ;
			else
				break ;
		}
		if( i == -1 )
		{
			printf("0\n") ;
			continue; 
		}
		for (i = strlen(s) - 1;i >= 0 ; i --)
		{
			if( s[i] == '.')
			{
				nRealCount = strlen(s) - i - 1 ;
				continue ;
			}
			number.nData[number.nLen++] = s[i] - '0' ;
		}


		tmp = number ;
		result.nData[0] = 1 ;
		result.nLen = 1 ;
		nRealCount *= n ;
		while( n > 1)
		{
			if( n & 1)
			{
				result = result * tmp  ;
				n -- ;
			}
			tmp = tmp * tmp ;
			n >>= 1 ;
		}
		result = result * tmp ;
		if( nRealCount >= result.nLen)
		{
			printf(".") ;
			for( i = 0 ; i < nRealCount - result.nLen ; i ++ )
				printf("0") ;
			for( i = result.nLen - 1 ; i >= 0 ; i --)
			{
				printf("%d",result.nData[i]) ;
			}
		}else 
		{
			for( i = result.nLen - 1; i >= 0 ; i --)
			{
				printf("%d",result.nData[i]) ;
				if(nRealCount != 0 && i == nRealCount)
					printf(".");
			}
		}
		printf("\n");


	}

	return 0 ;
}