forked from abbh07/DataStructure-Algorithms
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LRUCache.cpp
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LRUCache.cpp
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//http://practice.geeksforgeeks.org/problems/lru-cache/1
#include <iostream>
#include <vector>
#include <map>
#include <unordered_map>
#include <algorithm>
using namespace std;
class LRUCache
{
public:
LRUCache(int );
int get(int );
void set(int , int );
};
struct node
{
node* next;
node* prev;
int key;
int value;
};
unordered_map<int,node*> m;
int cap;
node *head = NULL;
node *last = NULL;
void remove(node* n)
{
if(n->prev != NULL)
{
n->prev->next = n->next;
}
else
{
head = n->next;
}
if(n->next != NULL)
{
n->next->prev = n->prev;
}
else
{
last = n->prev;
}
}
void setHead(node* n)
{
n->next = head;
n->prev = NULL;
if(head != NULL)
{
head->prev = n;
}
head = n;
if(last == NULL)
{
last = head;
}
}
/*Inititalize an LRU cache with size N */
LRUCache::LRUCache(int N)
{
::cap = N;
head = NULL;
last = NULL;
m.clear();
}
/*Sets the key x with value y in the LRU cache */
void LRUCache::set(int x, int y)
{
if(m.count(x)==1)
{
node *temp = m[x];
temp->value = y;
remove(temp);
setHead(temp);
}
else
{
node* n = new node();
n->key = x;
n->value = y;
n->next = n->prev = NULL;
if(m.size()>=cap)
{
m.erase(last->key);
remove(last);
setHead(n);
}
else
{
setHead(n);
}
m[x] = n;
}
}
/*Returns the value of the key x if
present else returns -1 */
int LRUCache::get(int x)
{
if(m.count(x) == 1)
{
node *n = m[x];
remove(n);
setHead(n);
return n->value;
}
else
{
return -1;
}
}
int main()
{
int t;
cin>>t;
while(t--)
{
int n;
cin>>n;
LRUCache *l = new LRUCache(n);
int q;
cin>>q;
for(int i=0;i<q;i++)
{
string a;
cin>>a;
if(a=="SET")
{
int aa,bb;
cin>>aa>>bb;
l->set(aa,bb);
}else if(a=="GET")
{
int aa;
cin>>aa;
cout<<l->get(aa)<<" ";
}
}
cout<<endl;
}
}