C++实现浮点数精确加法的实例详解

int main(){
 char num1[128],num2[128],res[128];
 cout<<"Enter the first number:";
 cin>>num1;
 cout<<"Enter the second number:";
 cin>>num2;
 add(num1,num2,res);
 cout<<num1<<'+'<<num2<<'='<<res<<endl;
 return 0;
}

#include <iostream>

using namespace std;

void add(char num1[], char num2[], char res[]);

int get_len(char num[]);

int get_integer(char num[]);

int get_dot(char num[]);

int get_decimal_len(char num[]);

int get_integer_len(int x);

int char_to_int(char num[], int begin, int len);

void int_to_char(char res[], int x);

void get_decimal(char num1[], char num2[]);

char decimal[128] = {0};

int main() {
 char num1[128] = {0}, num2[128] = {0}, res[128] = {0};
 cout << "Enter the first number:";
 cin >> num1;
 cout << "Enter the second number:";
 cin >> num2;
 add(num1, num2, res);
 cout << num1 << '+' << num2 << '=' << res << endl;
 return 0;
}

//获取小数点在哪一位
int get_dot(char num[]) {
 int i;
 for (i = 0; num[i] != '\0'; ++i) {
 if (num[i] == '.') {
 return i;
 }
 }
 return i;
}

//把字符串转化为整数
int char_to_int(char num[], int begins, int len) {
 int integer = 0, l = get_decimal_len(num);
 if (l < len) {
 for (int j = l; j <= len; ++j) {
 num[begins + j + 1] = '0';
 }
 }
 for (int i = 0; i < len; ++i) {
 integer = integer * 10 + num[begins + i + 1] - '0';
 }
 return integer;
}

//整数转化为字符串
void int_to_char(char res[], int x) {
 int i, l = get_integer_len(x);
 for (i = l - 1; i >= 0; --i) {
 res[i] = x % 10 + '0';
 x /= 10;
 }
 res[l + 1] = '\0';
}

//得到整数部分
int get_integer(char num[]) {
 int integer = 0, x = get_dot(num);
 for (int i = 0; i <= x - 1; ++i) {
 integer = integer * 10 + num[i] - '0';
 }
 return integer;
}

//得到小数部分长度
int get_decimal_len(char num[]) {
 int x = get_dot(num), len = 0;
 for (int i = x + 1; num[i] != '\0'; ++i)len++;
 return len;
}

//得到整数的长度
int get_integer_len(int x) {
 int integer_len = 0;
 if (x == 0)return 1;
 while (x > 0) {
 x /= 10;
 integer_len++;
 }
 return integer_len;
}

//得到字符串长度
int get_len(char num[]) {
 int sum = 0;
 for (int i = 0; num[i] != '\0'; ++i) sum++;
 return sum;
}

//得到小数变成整数后的和
void get_decimal(char num1[], char num2[]) {
 int decimal_len = get_decimal_len(num1) > get_decimal_len(num2) &#63; get_decimal_len(num1) : get_decimal_len(num2);
 int decimal_sum = char_to_int(num1, get_dot(num1), decimal_len) + char_to_int(num2, get_dot(num2), decimal_len);
 int_to_char(decimal, decimal_sum);
 if (decimal_len < get_integer_len(decimal_sum)) {
 for (int i = 0; decimal[i] != '\0'; ++i) {
 decimal[i] = decimal[i + 1];
 }
 }
}

void add(char num1[], char num2[], char res[]) {
 bool flag = false, zero_flag = false;
 int i;
 int l1 = get_len(num1), l2 = get_len(num2);
 get_decimal(num1, num2);
 int decimal_len = get_decimal_len(num1) > get_decimal_len(num2) &#63; get_decimal_len(num1) : get_decimal_len(num2);
 int decimal_sum = char_to_int(num1, get_dot(num1), decimal_len) + char_to_int(num2, get_dot(num2), decimal_len);
 if (decimal_len < get_integer_len(decimal_sum)) {
 flag = true;
 }
 int sum_int = get_integer(num1) + get_integer(num2) + flag;
 int_to_char(res, sum_int);
 *(res + get_integer_len(sum_int)) = '.';
 for (i = 1; decimal[i - 1] != '\0'; ++i) {
 *(res + get_integer_len(sum_int) + i) = decimal[i - 1];
 }
 for (i = get_dot(res) + 1; res[i] != '\0'; ++i) {
 if (res[i] != '0') {
 zero_flag = true;
 }
 }
 if (!zero_flag) {
 res[get_dot(res)] = '\0';
 } else {
 for (i = get_len(res) - 1; i > get_dot(res); --i) {
 if (res[i] == '0') {
 res[i] = '\0';
 break;
 }
 break;
 }
 }
 num1[l1] = '\0', num2[l2] = '\0';
}