题解 | #a+b#

#include <stdio.h>

int strlen(char a[]) {
    int res = 0;
    while (a[res] != '\0') {
        res++;
    }
    res--;
    return res;
}

int main() {
    char a[1000], b[1000];

    int i = 1001;
    while (scanf("%s %s", a, b) != EOF) {
        // a[0] = a[0] + 1;
        // printf("%s",a);
        int len_a = strlen(a);
        int len_b = strlen(b);
        int max = (len_a > len_b ? len_a : len_b);
        char res[max + 2];
        res[max + 1] = '\0';
        int j, flag  = 0;
        if (max == len_a) {
            j = len_b;
            for (int i = max; i >= 0; i--) {
                if (j == -1) {
                    if (a[i] + flag > '9') {
                        res[i + 1] = '0';
                        flag = 1;
                        j++;
                    } else {
                        res[i + 1] = a[i] + flag;
                        flag = 0;
                        j++;
                    }

                } else {
                    if (a[i] + b[j] - '0' + flag > '9') {
                        res[i + 1] = a[i] + b[j] - '0' + flag - 10;
                        flag = 1;
                    } else {
                        res[i + 1] = a[i] + b[j] - '0' + flag;
                        flag = 0;
                    }
                }
                j--;
            }
        } else {
            j = len_a;
            for (int i = max; i >= 0; i--) {
                if (j == -1) {
                    if (b[i] + flag > '9') {
                        res[i + 1] = '0';
                        flag = 1;
                        j++;
                    } else {
                        res[i + 1] = b[i] + flag;
                        flag = 0;
                        j++;
                    }
                } else {
                    if (b[i] + a[j] + flag - '0' > '9') {
                        res[i + 1] = b[i] + a[j] - '0' + flag - 10;
                        flag = 1;
                    } else {
                        res[i + 1] = b[i] + a[j] - '0' + flag;
                        flag = 0;
                    }
                }
                j--;
            }
        }
        if (flag == 1) {
            res[0] = '1';
            for (int i = 0; i <= max + 1; i++) {
                printf("%c", res[i]);
            }
            printf("\n");
        } else {
            for (int i = 1; i <= max + 1; i++) {
                printf("%c", res[i]);
            }
            printf("\n");
        }

    }
    return 0;
}