题解 | #判断两个IP是否属于同一子网#

#include "stdio.h"

int main()
{
    const int max = 255;
    const int cnt = 4;
    int ip[3][cnt];
    int i,j;
    int next[3] = {1,2,0};
    int out;

    while(scanf("%d.%d.%d.%d", &ip[i][0],&ip[i][1],&ip[i][2],&ip[i][3]) != EOF)
    {
        if(i == 2)
        {
            out = 0;//set to same

            for(j = 0;j<cnt;j++)
            {
                if((ip[0][j] > max) || (ip[1][j] > max)||(ip[2][j] > max) ||
                   (ip[0][j] < 0) || (ip[1][j] < 0)||(ip[2][j] < 0) ||
                  ((ip[0][j] != 255) && (j<3) &&(ip[0][j+1] != 0))
                  )
                {
                    out = 1;
                    break;
                }


                if((ip[0][j] & ip[1][j]) != (ip[0][j] & ip[2][j]))
                {
                    out = 2;//no break to check ip validation
                }
            }

            printf("%d\n", out);
        }

        i = next[i];
    }

    return 0;
}