Question

杭电3351为什么WA?跪求bug。。。

#include<stdio.h>
#include<string.h>
int head,tail;

int main(){
int Case,count;
char s[2001];
Case = 0;
while(scanf("%s",s),s[0] != '-')
{
Case ++;
head = 0;
tail = strlen(s) - 1;
count = 0;
while(head < tail)
{
if(s[head] != '{')
{
s[head] = '{';
count ++;
}
if(s[tail] != '}')
{
s[tail] = '}';
count ++;
}
while(head < tail && s[head] == '{' && s[head + 1] == '}')
head += 2;
while(head < tail && s[tail] == '}' && s[tail - 1] == '{')
tail -= 2;
if(head < tail && s[head] == '{' && s[tail] == '}')
{
head ++;
tail --;
}
}
printf("%d. %d\n",Case,count);
}
return 0;
}

Answer 1

{{}}{{}}

#include <stdio.h>
#include <string.h>

int main()
{
int Case, count;
int len, i, num;
char s[2001];
Case = 0;
while(scanf("%s",s),s[0] != '-')
{
Case++;
count = 0;
num = 0;
len = strlen(s);
for(i=0;i<len;i++)
{
if(s[i]=='{') num++;
else if(s[i]=='}')
if(num)
num--;
else
{
num++;
count++;
}
}
count += num/2;
printf("%d. %d\n",Case,count);
}
}