C++實作的一個簡單兩個大數相加程式！

#include <iostream>

using namespace std;

#define array_size 50

//enter a big number, and store it as a string into an array ch,

//the size is the numbers of char.

void inputnumbers(char ch[], int& size);

//reverse the elements of the array ch.

void reversearray(char ch[], int size);

//adding two big numbers, and the result will be stored in the array ch3,

//and return the size of the array ch3.

void computeadding(char ch1[], int size1, char ch2[], int size2, char ch3[], int& size3);

//show the adding result.

void displayresult(char ch[], int size);

int main()

{

char ch1[array_size], ch2[array_size], result[array_size];

int size1 = 0, size2 = 0, resultsize = 0;

cout << "enter the first big number, ending with an enter:" << endl;

inputnumbers(ch1, size1);

cout << "enter the second big number, ending with an enter:" << endl;

inputnumbers(ch2, size2);

reversearray(ch1, size1);

reversearray(ch2, size2);

computeadding(ch1, size1, ch2, size2, result, resultsize);

displayresult(result, resultsize);

system("pause");

    return 0;

}

//function inputnumbers

void inputnumbers(char ch[],  int& size)

char next;

    cin.get(next);

    while (next != '\n'  && size < array_size)

    {

          ch[size++] = next;

          cin.get(next);

    }

}//inputnumbers

//function reversearray

void reversearray(char ch[], int size)

int i = 0, j = size-1;

    char temp;

while (i <= j)

temp =  ch[i];

ch[i] = ch[j];

ch[j] = temp;

i ++;

j --;

}//end reversearray function

//function computeadding's definition

void computeadding(char ch1[], int size1, char ch2[], int size2, char ch3[], int& size3)

    int i,

          tmp,                  //as the temporary sum of two array elements.

          carrybit = 0;    //the carry-bit is initialized to zero

    for (i = 0; i < size1 && i < size2;  i++)

        tmp = (ch1[i]-'0') + (ch2[i]-'0') + carrybit;

        ch3[i] = tmp % 10 + '0';

        carrybit = tmp/10;

    while ( i<size1 ) { //if the array ch1 has more bits, execute this while loop.

        tmp = (ch1[i] - '0') + carrybit;

        carrybit = tmp / 10;

        i ++;

    while ( i < size2 ){

        tmp = (ch2[i] - '0') + carrybit;

        ch3[i] = tmp % 10 +'0';

    if( carrybit)

      ch3[i] = carrybit + '0';

      i ++;

     }

    ch3[i] = '\0';

    size3 = i;

}//end reversearray

//function displayresult

void displayresult(char ch[], int size)

reversearray(ch, size);//make the number to be normal

    cout << "the adding result is:" ;

for (int i = 0; i < size; i++)

   cout << ch[i] ;

    cout << endl;