Create Mo's Algo.cpp

Data Structure/Mo's Algo.cpp

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+const int MX = 2e5;   // query size . . .
+const int MXI = 1e6;  // maximum value in array . . .
+ll cnt[MXI+5];
+
+ll block_size, range_ans;
+
+struct Query{
+    int id, l, r;
+
+    Query() {}
+    Query(int _id, int _l, int _r){
+        id = _id;
+        l = _l;
+        r = _r;
+    }
+
+    bool operator<(Query &other) const{
+        int curr_size = l/block_size;
+        int other_size = other.l/block_size;
+
+        if(curr_size == other_size) return r < other.r;
+        return curr_size < other_size;
+    }
+} query[MX+5];
+
+void add(ll x)
+{
+    if(cnt[x]) range_ans -= cnt[x]*cnt[x]*x;
+    cnt[x]++;
+    range_ans += cnt[x]*cnt[x]*x;
+}
+void rmv(ll x)
+{
+    range_ans -= cnt[x]*cnt[x]*x;
+    cnt[x]--;
+    if(cnt[x]) range_ans += cnt[x]*cnt[x]*x;
+}
+ll get_solution()
+{
+    return range_ans;
+}
+
+void mos_algo()
+{
+    int n, t, l, r;
+
+    cin >> n >> t;
+
+    // setting block size ...
+    block_size = sqrt(n);
+
+    int ara[n];
+    for(int K = 0; K < n; K++) cin >> ara[K];
+
+    for(int K = 0; K < t; K++){
+        cin >> l >> r;
+
+        query[K] = Query(K, l-1, r-1); // 0-based indexing . . .
+    }
+    sort(query, query+t);
+
+    int L = 0, R = -1;
+    ll v[t];
+
+    for(int K = 0; K < t; K++){
+        l = query[K].l;
+        r = query[K].r;
+
+        while(L < l){
+            rmv(ara[L]);
+            L++;
+        }
+        while(L > l){
+            L--;
+            add(ara[L]);
+        }
+        while(R < r){
+            R++;
+            add(ara[R]);
+        }
+        while(R > r){
+            rmv(ara[R]);
+            R--;
+        }
+
+        v[query[K].id] = get_solution();
+    }
+
+    for(int K = 0; K < t; K++) cout << v[K] << "\n";
+}
+