DataStructureAndAlgorithm/1001/main.cpp

#include <stdio.h>

int main() {
    char a[1000] = {0};
    char b[1000] = {0};
    char result[1001] = {0};
    int a_index = 0, b_index = 0;
    int result_index = 0;
    char ch = getchar();
    while (ch != ' ') {
        a[a_index] = ch - '0';
        ch = getchar();
        a_index++;
    }

    a_index--;

    ch = getchar();
    while (ch != '\n' && ch != EOF && ch != ' ') {
        b[b_index] = ch - '0';
        ch = getchar();
        b_index++;
    }

    b_index--;

    if (a_index >= b_index) {
        while (a_index >= 0) {
            int current_digit = a[a_index] + b[b_index] + result[result_index];
            result[result_index] = current_digit % 10;
            result[++result_index] = current_digit / 10;
            a_index--;
            b_index--;
        }

        while (a_index >= 0) {
            int current_digit = a[a_index] + result[result_index];
            result[result_index] = current_digit % 10;
            result[++result_index] = current_digit / 10;
            a_index--;
        }
    }
    else {
        while (a_index >= 0) {
            int current_digit = a[a_index] + b[b_index] + result[result_index];
            result[result_index] = current_digit % 10;
            result[++result_index] = current_digit / 10;
            a_index--;
            b_index--;
        }

        while (b_index >= 0) {
            int current_digit = b[b_index] + result[result_index];
            result[result_index] = current_digit % 10;
            result[++result_index] = current_digit / 10;
            b_index--;
        }
    }

    if (result[result_index] == 0) {
        // The hightest digit is carry. There is a possibility that this digit is 0.
        result_index--;
    }

    while (result_index >= 0) {
        printf("%d", result[result_index]);
        result_index--;
    }

    return 0;
}