bignum-add-subtract

/*
 Author: 曹北健(37509)
 Result: AC Submission_id: 4121874
 Created at: Sun Mar 06 2022 10:47:42 GMT+0800 (China Standard Time)
 Problem: 5391  Time: 3 Memory: 1736
*/

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <math.h>
#include <string.h>
#pragma warning(disable:4996)
#define N 10
typedef long long LL;
typedef struct cbj0{
    short num[10020];
    char sgn;
    int len;
}bignum;
bignum A, B, *T;
char buf1[10020], buf2[10020];
int compabs(bignum *, bignum *);
bignum *add0(bignum *, bignum *);
bignum *subtract0(bignum *, bignum *);
bignum *add(bignum *, bignum *);
bignum *subtract(bignum *, bignum *);
void reverse(short *a, int n){
    int i, tmp;
    for(i = 0;i < n / 2;i++){
        tmp = a[i];
        a[i] = a[n - 1 - i];
        a[n - 1 - i] = tmp;
    }
}
void input(char *buf, bignum *a){
    int loc = 0;
    if(buf[0] == '-'){ a->sgn = '-'; loc++; }
    else a->sgn = '+';
    int cnt = 0, i;
    while(buf[loc] != '\0'){
        a->num[cnt] = buf[loc] - '0';
        loc++;cnt++;
    }
    for(i = cnt;i < 10020;i++)a->num[i] = 0;
    a->len = cnt;
    reverse(a->num, cnt);
}
int iszero(bignum *p){
    int i;
    for(i = p->len;i >= 0;i--){
        if(p->num[i] != 0)return 0;
    }
    return 1;
}
bignum *add(bignum *a, bignum *b){
    bignum *tmp;
    if(a->sgn == b->sgn){
        tmp = add0(a, b);
    }
    else{//异号
        if(compabs(a, b) >= 0){
            tmp = subtract0(a, b);
        }
        else{
            tmp = subtract0(b, a);
        }
    }
    return tmp;
}
int compabs(bignum *a, bignum *b){
    if(a->len > b->len)return 1;
    else{
        if(a->len < b->len)return -1;
        else{
            int i = a->len - 1;
            while(i >= 0){
                if(a->num[i] > b->num[i])return 1;
                if(a->num[i] < b->num[i])return -1;
                i--;
            }
            return 0;
        }
    }
}
bignum *add0(bignum *a, bignum *b){//ab同号
    int i = 0;
    while(i < a->len || i < b->len){
        short sum = 0;
        sum = (a->num[i]) + (b->num[i]);
        if(sum >= N){//进位
            a->num[i] = sum % N;
            a->num[i + 1] += sum / N;
        }
        else{
            a->num[i] = sum;
        }
        i++;
    }
    if(a->num[i] != 0){
        i++;
    }
    a->len = i;
    return a;
}
bignum *subtract0(bignum *a, bignum *b){//a>=b>=0
    int i = 0, cnt = 0;
    while(i < a->len){
        short tmp = a->num[i] - b->num[i];
        if(tmp < 0){
            a->num[i + 1] -= 1;
            a->num[i] = tmp + N;
        }
        else{
            a->num[i] = tmp;
        }
        cnt++;i++;
    }
    for(i = cnt - 1;i >= 0;i--){
        if(a->num[i] == 0){
            cnt--;
        }
        else{
            break;
        }
    }
    if(cnt == 0)cnt++;
    a->len = cnt;
    return a;
}
int main(){
#ifdef _DEBUG
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int i, p;//sgn为1表示正数 -1表示负数
    scanf("%d", &p);
    while(p--){
        memset(buf1, 0, sizeof(buf1));
        memset(buf2, 0, sizeof(buf2));
        scanf("%s%s", buf1, buf2);
        memset(&A, 0, sizeof(bignum));
        memset(&B, 0, sizeof(bignum));
        input(buf1, &A);
        input(buf2, &B);
        T = add(&A, &B);
        if(iszero(T)){
            printf("0\n");
        }
        else{
            if(T->sgn == '-'){ putchar('-'); }
            for(i = T->len - 1;i >= 0;i--){
                printf("%d", T->num[i]);
            }
            putchar('\n');
        }
    }
#ifdef _DEBUG
    freopen("CON", "r", stdin);
    freopen("CON", "w", stdout);
    system("pause");
#endif
    return 0;
}