The memset() function will initialize all of the memory within the t array to -1.
int t[constraint];
Solution(){
memset(t,-1,sizeof(t));
}
int solve(int n){
if(n==0)
return 1;
if(n<0) return 0;
if(t[n]!=-1) return t[n];
return t[n] = solve(n-1) + solve(n-2);
}