题解 | #数字字符串转化成IP地址#

/**
 * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
 *
 * 
 * @param s string字符串 
 * @return string字符串一维数组
 * @return int* returnSize 返回数组行数
 */
#include <stdlib.h>
#include <string.h>
#define isValid(a) (a >= 0 && a <= 255)
// bool isValid(int a) {
//     if(a >= 0 && a <= 255) return true;
//     return false;
// }

char** restoreIpAddresses(char* s, int* returnSize ) {
    // write code here
    int len = strlen(s);
    if(len < 4) return NULL;
    int dotP1, dotP2, dotP3;
    int i1 = 0,i2 = 0,i3 = 0,i4 = 0;
    *returnSize = 0;
    char** result = (char**)malloc(sizeof(char*));
    for(dotP1 = 1; dotP1 < 4; dotP1++) {
        char temp1[4];
        strncpy(temp1, s, dotP1);
        temp1[dotP1] = '\0';
        // printf("strncpy(temp, s, dotP1);的结果是%s\n", temp1);
        i1 = atoi(temp1);
        if(!isValid(i1)) continue;
        if(dotP1 > 1 && temp1[0] == '0' && temp1[1]) continue;
        for(dotP2 = dotP1 + 1; dotP2 < dotP1 + 4; dotP2++) {
            char temp2[4];
            strncpy(temp2, s + dotP1, dotP2 - dotP1);
            temp2[dotP2 - dotP1] = '\0';
            i2 = atoi(temp2);
            if(!isValid(i2)) continue;
            if(dotP2 - dotP1 > 1 && temp2[0] == '0' && temp2[1]) continue;
            for(dotP3 = dotP2 + 1; dotP3 < dotP2 + 4; dotP3++) {
                if(len - dotP3 <= 0 || len - dotP3 > 3) continue;
                char temp3[4];
                strncpy(temp3, s + dotP2, dotP3 - dotP2);
                temp3[dotP3 - dotP2] = '\0';
                i3 = atoi(temp3);
                if(!isValid(i3)) continue;
                if(dotP3 - dotP2 > 1 && temp3[0] == '0' && temp3[1]) continue;
                char temp4[4];
                strncpy(temp4, s + dotP3, len - dotP3);
                temp4[len - dotP3] = '\0';
                i4 = atoi(temp4);
                if(!isValid(i4)) continue;
                if(len - dotP3 > 1 && temp4[0] == '0' && temp4[1]) continue;
                // printf("%d.%d.%d.%d\n",i1,i2,i3,i4);
                result[(*returnSize)] = (char*)malloc(sizeof(char) * (len + 3));
                if(result[(*returnSize)] == NULL) {
                    for(int i = 0; i < *returnSize; i++) {
                        free(result[i]);
                    }
                    free(result);
                    return NULL;
                }
                sprintf(result[(*returnSize)], "%s.%s.%s.%s", temp1, temp2, temp3, temp4);
                (*returnSize)++;
                char** new_result = (char**)realloc(result, sizeof(char*) * ((*returnSize) + 1));
                if(new_result == NULL) {
                    for(int i = 0; i < *returnSize; i++) {
                        free(result[i]);
                    }
                    free(result);
                    return NULL;
                }
                result = new_result;
            }
        }
    }
    return result;
}