题解 | #识别有效的IP地址和掩码并进行分类统计#

#include <string.h>
#include <math.h>

/*
Name: maskIsIllegal
Desc: 判断子网掩码是否合法
Return: 0: 合法，非零：非法
*/
int maskIsIllegal(int *mask, int size)
{
    int result  = 0;
    int isMask = 0;
    int num;
//     printf("mask = %d.%d.%d.%d\n", mask[0], mask[1], mask[2], mask[3]);
    
    if(mask[0] == 255 && mask[1] == 255 && mask[2] == 255 && mask[3] == 255)
    {
        return -4;
    }
    for(int i = 0; i < size; i++)
    {
        num = mask[i];
        if(num != 0 && isMask != 0)    //掩码错误，...254.255情况
        {
            return -3;
        }
        
        if(num < 0 || num > 255)
        {
            return -2;
        }
        else if(num != 255)            //掩码不为 255置标志位
        {
            isMask = 1;
        }
        
        if(num == 0)
        {
            continue;
        }

        for(int j = 7; j >= 0; j--)
        {
            num -= pow(2, j);
            if(num == 0)
            {
                break;
            }
            if(num < 0)
            {
                return -1;
            }
            
        }
        
    }
    return result;
}

/*
Name: ipIsIllegal
Desc: 判断IP是否合法
Return: 0: 合法，非零：非法
*/
int ipIsIllegal(int *ip, int size)
{
    int ipNum;
//     printf("ip = %d.%d.%d.%d\n", ip[0],ip[1], ip[2], ip[3]);
    for(int i = 0; i < size; i++)
    {
        ipNum = ip[i];
        if(ipNum < 0 || ipNum > 255)
        {
            return -1;
        }
        
    }
    return 0;
}

int main()
{
    char input[32] = {0};
    int ip[4] = {-1};
    int mask[4] = {-1};
    int numA = 0, numB = 0, numC = 0, numD = 0, numE = 0, numErrIP = 0, numErrMask = 0, numPrivateIp = 0;
    int illegal = 0;
    
    while(scanf("%s",input) != EOF)
    {
        memset(ip, -1, 4);
        memset(mask, -1, 4);
        sscanf(input, "%d.%d.%d.%d~%d.%d.%d.%d", ip, ip + 1, ip + 2, ip + 3, mask, mask + 1, mask + 2, mask + 3);
        
        if(ip[0] == 0 || ip[0] == 127)
        {
            continue;
        }
        
        int errMaskCode = maskIsIllegal(mask, 4);
        int errIpCode = ipIsIllegal(ip, 4);
        
//         printf("errMaskCode = %d, errIpCode = %d \n", errMaskCode, errIpCode);
        if(errMaskCode != 0 ||  errIpCode != 0)
        {
//             illegal++;
            numErrMask++;
            continue;
        }
        
        if(ip[0] == -1 || ip[1] == -1 || ip[2] == -1 || ip[3] == -1)
        {
            numErrIP++;
        }
        else if(ip[0] >= 1 && ip[0] <= 126)        //A类
        {
            numA++;
            if(ip[0] == 10)                //第一种私网络IP 10.0.0.0到10.255.255.255
            {
                numPrivateIp++;
            }
        }
        else if(ip[0] >= 128 && ip[0] <= 191)        //B类
        {
            numB++;
            if(ip[0] == 172 && ip[1] >= 16 && ip[1] <= 31)    //第二种私有网络IP 172.16.0.0到172.31.255.255
            {
                numPrivateIp++;
            }
        }
        else if(ip[0] >= 192 && ip[0] <= 223)        //C类
        {
            numC++;
            if(ip[0] == 192 && ip[1] == 168)            //第三种私有网络IP 192.168.0.0到192.168.255.255
            {
                numPrivateIp++;
            }
        }
        else if(ip[0] >= 224 && ip[0] <= 239)        //D类
        {
            numD++;
        }
        else if(ip[0] >= 240 && ip[0] <= 255)        //E类
        {
            numE++;
        }
        
    }
    
    printf("%d %d %d %d %d %d %d", numA, numB, numC, numD, numE, numErrMask, numPrivateIp);
    return 0;
}