A+B Problem Plus and A-B Problem Plus and A*B Problem Plus

//we have defined the necessary header files here for this problem.
//If additional header files are needed in your program, please import here.

#include <stdio.h>
#include <string.h>

#define LENGHT 1000

void sumPlus(char *a, char *b);

void reverse(char *a);

int main() {
    int times;
    scanf("%d", &times);
    char operator[][LENGHT] = {{''},
                                {''}};
    for (int i = ; i < times; ++i) {
        scanf("%s %s", operator[], operator[]);
        printf("Case %d:\n", i + );
        printf("%s + %s = ", operator[], operator[]);
        sumPlus(operator[], operator[]);
        if (i != times - ) {
            printf("\n");
            printf("\n");
        }
    }
    return ;
}

void sumPlus(char *a, char *b) {
    int res[LENGHT + ] = {};
    reverse(a);
    reverse(b);
    int flag_a = , flag_b = , carry = ;  //进位
    for (int i = ; i < LENGHT; ++i) {
        int x = , y = ;
        if (a[i] == '\0')
            flag_a = ;
        if (b[i] == '\0')
            flag_b = ;
        if (!flag_a) {
            x = a[i] - '';
        }
        if (!flag_b) {
            y = b[i] - '';
        }
        int temp = x + y + carry; //字符类型转int类型
        res[i] = temp % ;
        carry = temp / ;
    }
    int i = LENGHT;
    while (res[i] == ) {
        i--;
    }
    while (i >= ) {
        printf("%d", res[i]);
        i--;
    }
}

void reverse(char *a) {
    int size = strlen(a);
    char temp[LENGHT + ] = {''};
    for (int i = size - , j = ; i >= ; --i, ++j) {
        temp[j] = a[i];
    }
    memcpy(a, temp, size);
//    a[size] = '\0';
}

---

#include <stdio.h>
#include <string.h>
#define MAX_LEN 1001
void removeZero(char *result, char *input)
{
    int len = strlen(input);
    for(int i = ; i < len; ++i) {
        if(input[i] == '') {
            continue;
        }
        strncpy(result, input+i, len-i);
        result[len-i] = '\0';
        return;
    }
    strcpy(result, "");
}
int compare(char *numA, char *numB)
{
    int lenA = strlen(numA);
    int lenB = strlen(numB);
    if(lenA != lenB) {
        return lenA - lenB;
    }
    for(int i = ; i < lenA; ++i) {
        if(numA[i] < numB[i]) {
            return -;
        }
        if(numA[i] > numB[i]) {
            return ;
        }
    }
    return ;
}
void sub(char *numA, char *numB, char *result)
{
    int lenA = strlen(numA);
    int lenB = strlen(numB);
    int offset = lenA - lenB;
    char numBCopy[MAX_LEN];
    strcpy(numBCopy, numB);
    if(offset) {
        for(int i = lenB-; i >= ;--i) {
            numB[i+offset] = numB[i];
        }
        for(int i = ;i < offset;++i) {
            numB[i] = '';
        }
    }
    // calculate
    int carry = ;
    for(int i = lenA-; i >= ; --i) {
        int value = numA[i] - numB[i] - carry;
        if(value < ) {
            result[i] = '' + ( + value);
            carry = ;
        } else {
            result[i] = '' + value;
            carry = ;
        }
    }
    result[lenA] = '\0';
    strcpy(numB, numBCopy);
}
void minus(char *numA, char *numB, char *result)
{
    char number[MAX_LEN];
    int ret = compare(numA, numB);
    if(ret == ) {
        strcpy(result, "");
        return;
    }
    char removeZeroStr[MAX_LEN];
    if(ret < ) {
        sub(numB, numA, number);
        removeZero(removeZeroStr, number);
        sprintf(result, "-%s", removeZeroStr);
    } else {
        sub(numA, numB, number);
        removeZero(removeZeroStr, number);
        strcpy(result, removeZeroStr);
    }
}
int main()
{
    int N;
    char a[MAX_LEN], b[MAX_LEN];
    while(scanf("%d", &N) != EOF) {
        for(int i = ; i < N; ++i) {
            scanf("%s", a);
            scanf("%s", b);
            char result[MAX_LEN+];
            minus(a, b, result);
            printf("Case %d:\n", i+);
            printf("%s - %s = %s\n\n", a, b, result);
        }
    }
    return ;
}

---

#include <stdio.h>
#include <string.h>

#define LENGTH 1001
#define RESLENGTH 2002
void multiply(char *a, char *b, int length_a, int length_b);

int main() {
    char a[LENGTH] = "\0";
    char b[LENGTH] = "\0";
    int len_a, len_b;
    while (scanf("%s %s", a, b) != EOF) {
        len_a = strlen(a);
        len_b = strlen(b);
        multiply(a, b, len_a, len_b);
        printf("\n");
    }
    return ;
}

void multiply(char *a, char *b, int length_a, int length_b) {
    int res_len = length_a + length_b;
    int res[RESLENGTH] = {};
    for (int i = ; i < length_a; ++i) {
        for (int j = ; j < length_b; ++j) {
            res[i + j] += (a[length_a - i - ] - '') * (b[length_b - j - ] - '');  //字符转整数
        }
    }
    for (int k = ; k < res_len; ++k) {
        if (res[k] >= ) {
            res[k + ] += res[k] / ;
            res[k] = res[k] % ;
        }
    }

    //去掉头部的0
    int index = res_len;
    while(res[index]== && index>=){
        index--;
    }
    if(index<){
        printf("");
        return;
    }
    for (int i = index; i >= ; --i) {
        printf("%d", res[i]);
    }

}