Create even_odd_numbers_in_range.cpp

Author: h4wwk3ye

fenwick_tree/even_odd_numbers_in_range.cpp

@@ -0,0 +1,103 @@
+// https://www.hackerearth.com/practice/data-structures/advanced-data-structures/fenwick-binary-indexed-trees/practice-problems/algorithm/help-ashu-1/
+
+/*
+				C++
+				encoding: UTF-8
+				Modified: <03/Oct/2019 04:18:08 PM>
+
+				✪ H4WK3yE乡
+				Mohd. Farhan Tahir
+				Indian Institute Of Information Technology (IIIT), Gwalior
+*/
+
+#include <bits/stdc++.h>
+#ifdef LOCAL_PROJECT
+#	include <prettypr.hpp>
+#endif
+
+using namespace std;
+
+// clang-format off
+
+#define         ll                     long long
+#define         ve                     vector
+#define         pb                     push_back
+#define         endl                   "\n"
+#define         ff                     first
+#define         ss                     second
+#define         pii                    pair<int, int>
+#define         len(v)                 int(v.size())
+#define         all(v)                 v.begin(), v.end()
+#define         reset(a, b)            memset(a, b, sizeof(a));
+#define         fr(i, s, n)            for (int i = s ; i < n ; ++i)
+#define         dfr(i, s, n)           for (int i = s ; i > n ; --i)
+
+template < typename T > void pr (const T& t) {
+    cout << t << "\n";
+}
+
+template < typename T, typename U, typename... ARGS >
+void pr (const T& t, const U& u, const ARGS&... args) {
+    cout << t << " ";
+    pr (u, args...);
+}
+
+// clang-format on
+
+const int N = 1e5 + 5;
+int arr[N];
+int bit[N];
+int n;
+
+void update (int x, int val) {
+	while (x <= n) {
+		bit[x] += val;
+		x += (x & (-x));
+	}
+}
+
+int query (int x) {
+	int ans = 0;
+	while (x > 0) {
+		ans += bit[x];
+		x -= (x & (-x));
+	}
+	return ans;
+}
+
+int query (int l, int r) {
+	return query (r) - query (l - 1);
+}
+
+signed main () {
+	ios_base::sync_with_stdio (false), cin.tie (nullptr);
+	cin >> n;
+	fr (i, 1, n + 1) {
+		cin >> arr[i];
+		arr[i] &= 1;
+		if (!arr[i]) update (i, 1);
+	}
+	int tc;
+	cin >> tc;
+	while (tc--) {
+		int t, x, y;
+		cin >> t >> x >> y;
+		if (t == 0) {
+			y &= 1;
+			if (arr[x] and !y) {
+				update (x, 1);
+			}
+			if (!arr[x] and y) {
+				update (x, -1);
+			}
+			arr[x] = y & 1;
+		} else if (t == 1) {
+			int ans = query (x, y);
+			pr (ans);
+		} else {
+			int ans = query (x, y);
+			pr (y - x + 1 - ans);
+		}
+	}
+	return 0;
+}