题解 | #合法IP#

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int num(char n){
    if(n>='0'&&n<='9') return 1;
    else return 0;
}

int main() {
    char a1[19]={0}, b1[19]={0},c1[19]={0},d1[19]={0},e1[19]={0};
        scanf("%[^.].%[^.].%[^.].%[^\nor^.].%[^\n]", a1,b1,c1,d1,e1);
        int a2=strlen(a1),b2=strlen(b1),c2=strlen(c1),d2=strlen(d1),e2=strlen(e1);
        if(a2==0||b2==0||c2==0||d2==0||e2!=0) printf("NO");
        else
        {int a,b,c,d;
        a=atoi(a1);
         b=atoi(b1);
          c=atoi(c1);
           d=atoi(d1);
        if(a>255||a<0||b>255||b<0||c>255||c<0||d>255||d<0)
        printf("NO");
        else if((a1[0]=='0'&&num(a1[1]))||(b1[0]=='0'&&num(b1[1]))||(c1[0]=='0'&&num(c1[1]))||(d1[0]=='0'&&num(d1[1])))
        printf("NO");
        else if(num(a1[0])==0||num(b1[0])==0||num(c1[0])==0||num(d1[0])==0)
        printf("NO");
        else printf("YES");}
    return 0;
}