题解 | #高精度整数加法#

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_LEN 10001

void add(char* str1, char* str2) {
    int len1 = strlen(str1), len2 = strlen(str2);
    int longer = len1 > len2 ? len1 : len2;
    int i = len1 - 1, j = len2 - 1, k = longer, carry = 0;
    int* result = (int*)malloc((longer + 1) * sizeof(int));
    while (i >= 0 && j >= 0) {
        int sum = str1[i--] - '0' + str2[j--] - '0' + carry;
        result[k--] = sum % 10;
        carry = sum / 10;
        // printf("when i >= 0 j >= 0, i is %d, j is %d, k is %d,sum = %d, result = %d, carry is %d\n", i+1, j+1, k+1,sum, result[k+1], carry);
    }
    while (i >= 0) {
        int sum = str1[i--] - '0' + carry;
        result[k--] = sum % 10;
        carry = sum / 10;
        // printf("when i >= 0,i is %d, k is %d,sum = %d, result = %d, carry is %d\n", i+1,k+1,sum, result[k+1], carry);
    }
    while (j >= 0) {
        int sum = str2[j--] - '0' + carry;
        result[k--] = sum % 10;
        carry = sum / 10;
        // printf("when j >= 0,j is %d, k is %d,sum = %d, result = %d, carry is %d\n", j+1,k+1,sum, result[k+1], carry);
    }
    if(carry > 0) {
        result[k] = carry;
    } else {
        k++;
    }
    for(i = k; i <= longer; i++) {
        printf("%d",result[i]);
    }
    printf("\n");
    free(result);
}

int main() {
    char str1[MAX_LEN], str2[MAX_LEN];
    while(scanf("%s\n%s", str1, str2) != EOF) {
        add(str1, str2);
    }
    return 0;
}