Merge pull request #518 from MANISH-BEESA/day9-q1

added day 9 q1 solution

Author: Dheeraj-06

Problems/Data-structures/Day-09/sol/BEESA-MANISH/Solution1.cpp

@@ -0,0 +1,76 @@
+/*
+Submission link - https://cses.fi/problemset/result/15829712/
+
+TC - o((N + Q) log(N+Q) )
+SC - O(N + Q)
+
+Approach (Simple & Short):
+
+Compress salary values since they can be as large as 10^9.
+Use a Fenwick Tree to store and manage salary frequencies.
+On updates, reduce the count of the old salary and increase the new one.
+For range queries, get the answer using prefix sums from the Fenwick Tree.
+
+*/
+
+
+#include <bits/stdc++.h>
+using namespace std;
+const int N = 600005;
+int n, q;
+int cur_p[200005];
+int t[N];
+struct Query {
+    int type, a, b;
+} qs[200005];
+ 
+void add(int i, int v) {
+    for (; i < N; i += i & -i) t[i] += v;
+}
+ 
+int sum(int i) {
+    int s = 0;
+    for (; i > 0; i -= i & -i) s += t[i];
+    return s;
+}
+ 
+int main() {
+    ios::sync_with_stdio(0); cin.tie(0);
+    cin >> n >> q;
+    vector<int> coords;
+    for (int i = 1; i <= n; i++) {
+        cin >> cur_p[i];
+        coords.push_back(cur_p[i]);
+    }
+    for (int i = 0; i < q; i++) {
+        char op; cin >> op;
+        cin >> qs[i].a >> qs[i].b;
+        if (op == '!') {
+            qs[i].type = 1;
+            coords.push_back(qs[i].b);
+        } else {
+            qs[i].type = 2;
+            coords.push_back(qs[i].a);
+            coords.push_back(qs[i].b);
+        }
+    }
+    sort(coords.begin(), coords.end());
+    coords.erase(unique(coords.begin(), coords.end()), coords.end());
+ 
+    auto get_idx = [&](int x) {
+        return lower_bound(coords.begin(), coords.end(), x) - coords.begin() + 1;
+    };
+ 
+    for (int i = 1; i <= n; i++) add(get_idx(cur_p[i]), 1);
+ 
+    for (int i = 0; i < q; i++) {
+        if (qs[i].type == 1) {
+            add(get_idx(cur_p[qs[i].a]), -1);
+            cur_p[qs[i].a] = qs[i].b;
+            add(get_idx(cur_p[qs[i].a]), 1);
+        } else {
+            cout << sum(get_idx(qs[i].b)) - sum(get_idx(qs[i].a) - 1) << "\n";
+        }
+    }
+    return 0;
+}