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HJ39判断两个IP是否属于同一子网

news 2025/7/7 19:54:25

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文章目录

前言
一、背景
二、
- 2.1
- 2.2
总结

前言

HJ39判断两个IP是否属于同一子网

一、代码：

第一版代码没有对掩码网络号进行处理。一开始对非法字段的理解就是value大于255。然后执行示例，

254.255.0.0
85.122.52.249
10.57.28.117

1

2

出现错误，增加修改为掩码只能是255和0这两个，跑了下面的代码，还是有示例没有通过。

#include <stdio.h>
#include <stdlib.h>int main() {int a, b;char sonNet[20] = {'\0'};char ip1[20] = {'\0'};char ip2[20] = {'\0'};int arraySonNet[4] = {0};int arrayIp1[4] = {0};int arrayIp2[4] = {0};while (scanf("%s", sonNet) != EOF) { // 注意 while 处理多个 case// 64 位输出请用 printf("%lld") to char output = 'f';char delimiters[2] = ".";char* p = strtok(sonNet, delimiters);int index = 0;while(p != NULL){//printf("%s\n", p);int data = atoi(p);if(data > 255){output = '1';break;}else if(data != 255 && data != 0){output = '1';break;}arraySonNet[index++] = data;p = strtok(NULL, delimiters);}if(scanf("%s", ip1) != EOF){p = strtok(ip1, delimiters);int index = 0;while(p != NULL){//printf("%s\n", p);int data = atoi(p);if(data > 255){output = '1';break;}arrayIp1[index++] = data;p = strtok(NULL, delimiters);}}if(scanf("%s", ip2) != EOF){p = strtok(ip2, delimiters);int index = 0;while(p != NULL){//printf("%s\n", p);int data = atoi(p);if(data > 255){output = '1';break;}arrayIp2[index++] = data;p = strtok(NULL, delimiters);}}int count = 0;for(int i = 0; i < 4; i++){if( (ip1[i] & sonNet[i]) == (ip2[i] & sonNet[i]) ){++count;}}if(output == 'f'){if(count == 4){output = '0';}else {output = '2';}}printf("%c\n", output);}return 0;
}

255.255.252.0
173.225.245.45
69.138.93.228

2

1

这个示例没有通过。然后我仔细看了下题目对于掩码非法的说明。其中有这句话：掩码的二进制字符串前缀为网络号，都由‘1’组成；后缀为主机号，都由’0’组成。

这边涉及到掩码的网络号的问题，还需要单独处理一下逻辑。

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>bool isTargetSonNet(int array[], int len)
{int tempArray[32] = {0};int tempArrayIndex = 0;for(int i = 0; i < len; i++){int data = array[i];if(data > 255){return false;}int index = ((tempArrayIndex + 1) * 8);while(data){int dat = data % 2;tempArray[--index] = dat;data /= 2;}tempArrayIndex++;}int count = 0;for(int i = 0; i < 32; i++){int temp = tempArray[i] - tempArray[i + 1];if(temp == 1){count++;}}if(count != 1){return false;}return true;
}int main() {int a, b;char sonNet[20] = {'\0'};char ip1[20] = {'\0'};char ip2[20] = {'\0'};int arraySonNet[4] = {0};int arrayIp1[4] = {0};int arrayIp2[4] = {0};while (scanf("%s", sonNet) != EOF) { // 注意 while 处理多个 case// 64 位输出请用 printf("%lld") to char output = 'f';char delimiters[2] = ".";char* p = strtok(sonNet, delimiters);int index = 0;while(p != NULL){//printf("%s\n", p);int data = atoi(p);// if(data > 255)// {//     output = '1';//     break;// }// else if(data != 255 && data != 0)// {//     output = '1';//     break;// }arraySonNet[index++] = data;p = strtok(NULL, delimiters);}if(!isTargetSonNet(arraySonNet, 4)){output = '1';}if(scanf("%s", ip1) != EOF){p = strtok(ip1, delimiters);int index = 0;while(p != NULL){//printf("%s\n", p);int data = atoi(p);if(data > 255){output = '1';break;}arrayIp1[index++] = data;p = strtok(NULL, delimiters);}}if(scanf("%s", ip2) != EOF){p = strtok(ip2, delimiters);int index = 0;while(p != NULL){//printf("%s\n", p);int data = atoi(p);if(data > 255){output = '1';break;}arrayIp2[index++] = data;p = strtok(NULL, delimiters);}}int count = 0;for(int i = 0; i < 4; i++){if( (ip1[i] & sonNet[i]) == (ip2[i] & sonNet[i]) ){++count;}}if(output == 'f'){if(count == 4){output = '0';}else {output = '2';}}printf("%c\n", output);}return 0;
}

以为上面的版本会通过，不过下面的示例还是没有通过

1.255.255.0
187.39.235.7
219.79.189.231
1
2

增加对isTargetStr函数的逻辑处理

bool isTargetSonNet(int array[], int len)
{int tempArray[32] = {0};int tempArrayIndex = 0;for(int i = 0; i < len; i++){int data = array[i];if(data > 255){return false;}int index = ((tempArrayIndex + 1) * 8);while(data){int dat = data % 2;tempArray[--index] = dat;data /= 2;}tempArrayIndex++;}int count = 0;for(int i = 0; i < 32; i++){int temp = tempArray[i] - tempArray[i + 1];if(temp != 0 && temp != 1){return false;}if(temp == 1){count++;}}if(count != 1){return false;}return true;
}

还是没有通过全部示例

255.0.0.0
193.194.202.15
232.43.7.59

2

1

修改isTargetStr函数如下

bool isTargetSonNet(int array[], int len)
{int tempArray[32] = {0};int tempArrayIndex = 0;for(int i = 0; i < len; i++){int data = array[i];if(data > 255){return false;}int index = ((tempArrayIndex + 1) * 8);while(data){int dat = data % 2;tempArray[--index] = dat;data /= 2;}tempArrayIndex++;}int count = 0;for(int i = 0; i + 1 < 32; i++){int temp = tempArray[i] - tempArray[i + 1];if(temp != 0 && temp != 1){return false;}if(temp == 1){count++;}}if(count != 1){return false;}return true;
}

主要是这一行： for(int i = 0; i + 1 < 32; i++)

修改后示例报错

255.255.255.0
167.-79.164.247
158.201.137.151

1

2

将isTragetStr函数改成下述形式

bool isTargetSonNet(int array[], int len)
{int tempArray[32] = {0};int tempArrayIndex = 0;for(int i = 0; i < len; i++){int data = array[i];if(data > 255 || data < 0){return false;}int index = ((tempArrayIndex + 1) * 8);while(data){int dat = data % 2;tempArray[--index] = dat;data /= 2;}tempArrayIndex++;}int count = 0;for(int i = 0; i + 1 < 32; i++){int temp = tempArray[i] - tempArray[i + 1];if(temp != 0 && temp != 1){return false;}if(temp == 1){count++;}}if(count != 1){return false;}return true;
}