Merge pull request #536 from prashant2007-wq/main

Update contributers.md

Author: zonedoutdg

Problems/Data-structures/Day-09/sol/prashant/solution2.cpp

@@ -0,0 +1,110 @@
+// ----------------------------------------------------------------------
+//                   ██████╗ ██████╗ ██████╗ ███████╗
+//                  ██╔════╝██╔═══██╗██╔══██╗██╔════╝
+//                  ██║     ██║   ██║██║  ██║█████╗
+//                  ██║     ██║   ██║██║  ██║██╔══╝
+//                  ╚██████╗╚██████╔╝██████╔╝███████╗
+//                   ╚═════╝ ╚═════╝ ╚═════╝ ╚══════╝
+// ----------------------------------------------------------------------
+//                       Prashant'S CP TEMPLATE
+//                       "Think. Code. Conquer."
+// ----------------------------------------------------------------------
+#include<iostream>
+#include<vector>
+#include<algorithm>
+#include<unordered_map>
+#include<bit>
+#include<map>
+#include<set>
+#include<queue>
+#include<stack>
+#include<string>
+#include<iterator>
+#include<cmath>
+#include<iomanip>
+#include<climits>
+#include<cstdint>
+#include<cstdlib>
+using namespace std;
+#define ll long long
+#define int long long
+#define MOD 1000000007
+#define pb push_back
+#define all(v) v.begin(),v.end()
+#define rall(v) v.rbegin(),v.rend()
+#define sz(x) (int)(x).size()
+#define srt(v) sort(v.begin(),v.end())
+#define Rsrt(v) sort(v.begin(),v.end(),greater<int>())
+#define endl "\n"
+#define F first
+#define S second
+#define vi vector<int>
+#define vc vector<char>
+#define vb vector<bool>
+#define vvi vector<vector<int>>
+#define pii pair<int,int>
+#define umap unordered_map
+#define mii map<int,int>
+#define fr(i,a,b) for(int i=a;i<b;i++)
+#define frr(i,a,b) for(int i=a;i>b;i--)
+#define mxe(v) *max_element(v.begin(),v.end())
+#define mne(v) *min_element(v.begin(),v.end())
+class FenwickTree{
+    public:
+    vi tree;
+    int n;
+    FenwickTree(int size){
+        n=size;
+        tree.assign(n+1,0);
+    }
+    void update(int idx,int val){
+        while(idx<=n){
+            tree[idx]+=val;
+            idx+=idx&(-idx);
+        }
+    }
+    int query(int idx){
+        int sum=0;
+        while(idx>0){
+            sum+=tree[idx];
+            idx-=idx&(-idx);
+        }
+        return sum;
+    }
+};
+signed main(){
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+    int n;
+    cin>>n;
+    vi a(n);
+    fr(i,0,n) cin>>a[i];
+    vi sorted_a=a;
+    srt(sorted_a);
+    map<int,int> compress;
+    fr(i,0,n){
+        compress[sorted_a[i]]=i+1;
+    }
+    vi compressed(n);
+    fr(i,0,n){
+        compressed[i]=compress[a[i]];
+    }
+    vi leftGreater(n);
+    FenwickTree ft1(n);
+    fr(i,0,n){
+        leftGreater[i]=i-ft1.query(compressed[i]);
+        ft1.update(compressed[i],1);
+    }
+    vi rightSmaller(n);
+    FenwickTree ft2(n);
+    frr(i,n-1,-1){
+        rightSmaller[i]=ft2.query(compressed[i]-1);
+        ft2.update(compressed[i],1);
+    }
+    int answer=0;
+    fr(i,0,n){
+        answer+=leftGreater[i]*rightSmaller[i];
+    }
+    cout<<answer<<endl;
+    return 0;
+}