uva 748 Exponentiation 浮点数乘方运算 高精度水题

输入的前六位数表示一个小数，然后输入一个数表示几次方。要求用高精度算出结果。

高精度水题，主要注意处理小数点，先在输入时把小数点提取出来并记录位置，用普通乘法计算出结果后由后向前计算位置添加小数点。

代码：

 

#include <cstdio>

#include <cstring>



const int maxn = 300;



void Mul(char *str1, char *str2, char *str3){ 

	int  i, j, i1, i2, tmp, carry, jj; 

	int  len1 = strlen(str1), len2 = strlen(str2); 

	char  ch; 



	jj = carry = 0; 



	for( i1=len1-1; i1 >= 0; --i1 ){ 

		j = jj; 

		for( i2=len2-1; i2 >= 0; --i2, ++j ){ 

			tmp = 

				(str3[j]-'0')+(str1[i1]-'0')*(str2[i2]-'0')+carry; 

			if( tmp > 9 ){ 

				carry = tmp/10; str3[j] = tmp%10+'0'; 

			} 

			else { 

				str3[j] = tmp+'0'; carry = 0; 

			} 

		} 

		if( carry ) { 

			str3[j] = carry+'0'; carry = 0; ++j; 

		} 

		++jj; 

	} 

	--j; 

	while( str3[j] == '0' && j > 0 ) --j; 

	str3[++j] = '\0'; 

	for( i=0, --j; i < j; ++i, --j ){ 

		ch = str3[i]; str3[i] = str3[j]; str3[j] = ch; 

	} 

}



int main() {

	char num[maxn], res[maxn], t[maxn];

	int n;

	while (1) {

		int p, tmp, i = 0;

		while ((tmp = getchar()) != EOF && tmp != ' ')

			if (tmp == '.')

				p = i;

			else{

				t[i]= num[i] = tmp;

				i++;

			}

		for (int j = i - 1; j >= 0; j--)

			if (num[j] != '0') {

				i = j + 1;

				break;

			}

		t[i] = num[i] = '\0';

		if (scanf("%d", &n) == EOF)

			break;

		p = (strlen(num) - p) * n;

		getchar();

		memset(res, '0', sizeof(res));

		for (int i = 0; i < n - 1; i++) {

			Mul(num, t, res);

		//	if (i == n - 1)

		//	   	printf("%s %s %s\n", num, t, res);

		//printf("hehe\n%s\n", res);

			if (i != n - 2) 

			for (int j = 0; j < maxn; j++) {

				t[j] = res[j];

			   	res[j] = '0';

			}

		}

		if (p >= strlen(res)) {

			printf(".");

			for (int i = 0; i < p - strlen(res); i++)

				printf("0");

			printf("%s\n", res);

		}

		else {

			int i;

			for (i = 0; i < strlen(res) - p; i++)

				printf("%c", res[i]);

			printf(".");

			printf("%s\n", res + strlen(res) - p);

		}

	}

	return 0;

}