UVA 11988 Broken Keyboard (a.k.a. Beiju Text)

#include<stdio.h>
#include<string.h>
#define MAXD 100010
int L[MAXD], R[MAXD];
char b[MAXD];
void solve()
{
int i, j, k;
L[0] = R[0] = 0;
for(i = 1; b[i]; i ++)
{
if(b[i] == '[')
L[i] = 0, R[i] = R[0];
else if(b[i] == ']')
L[i] = L[0], R[i] = 0;
else
L[i] = i - 1, R[i] = R[i - 1];
L[R[i]] = i, R[L[i]] = i;
}
for(i = R[0]; i != 0; i = R[i]) if(b[i] != '[' && b[i] != ']') printf("%c", b[i]);
printf("\n");
}
int main()
{
while(gets(b + 1) != NULL)
solve();
return 0;
}