int par[1<<20][21], size[1<<20], kth, Q;
char a[1<<20];
void Init(){}
void TypeLetter(char x)
{
if(kth) par[kth][0] = kth - 1;
for(int i = 1; par[kth][i-1]; i++)
{
par[kth][i] = par[par[kth][i-1]][i-1];
}
a[kth] = x, size[kth] = size[par[kth][0]] + 1, kth++;
}
void UndoCommand(int x)
{
par[kth][0] = kth - x - 1;
for(int i = 1; par[kth][i-1]; i++)
{
par[kth][i] = par[par[kth][i-1]][i-1];
}
a[kth] = a[par[kth][0]], size[kth] = size[par[kth][0]], kth++;
}
char GetLetter(int x)
{
int u = kth - 1;
for(int i = 19; i + 1; i--)
{
if(size[par[u][i]] > x) u = par[u][i];
}
return a[u];
}
Compilation message
/tmp/ccWTkxvi.o: In function `main':
grader.cpp:(.text.startup+0x14b): undefined reference to `UndoCommands(int)'
collect2: error: ld returned 1 exit status
