PAT考试乙级1014(C语言实现) 部分正确

#include<stdio.h>
#include <string.h>
int main(){
int i,l1,l2;
char s1[61],s2[61],s3[61],s4[61];
scanf("%s%s%s%s",s1,s2,s3,s4);
l1 = strlen(s1)<strlen(s2)?strlen(s1):strlen(s2);
l2 = strlen(s3)<strlen(s4)?strlen(s3):strlen(s4);
if(s1!=NULL&&s2!=NULL&&s3!=NULL&&s4!=NULL){
for(i=0;i<l1;++i){
if(s1[i]==s2[i]&&s1[i]>='A'&&s1[i]<='D'){
switch(s1[i]){
case 'A':
printf("MON"); break;
case 'B':
printf("TUE"); break;
case 'C':
printf("WED"); break;
case 'D':
printf("THU"); break;
case 'E':
printf("FRI"); break;
case 'F':
printf("SAT"); break;
case 'G':
printf("SUN"); break;
}
break;
}
}

for(i=i+1;i<l1;++i){
if( s1[i]==s2[i] && ( (s1[i]>='0'&&s1[i]<='9')||(s1[i]>='A'&&s1[i]<='N') ) ){
if('0'<=s1[i]&&s1[i]<='9'){
printf(" 0%d:",s1[i]-48);
}else{
printf(" %d:",s1[i]-'A'+10);
}
break;
}
}

for(i=0;i<l2;++i){
if(s3[i]==s4[i]&&((s3[i]>='a'&&s3[i]<='z')||(s3[i]>='A'&&s3[i]<='Z'))){
if(i<10){
printf("0%d",i);
}else{
printf("%d",i);
}
break;
}
}

}
}