unordered_map sometimes better than map:

got TLE with map on Collecting_Numbers_II.cpp but AC with unordered_map
-unordered is good for a lot of requests and a lot of data

CSES - CSES Problem Set/Collecting_Numbers.cpp

@@ -0,0 +1,19 @@
+//  Collecting Numbers
+
+#include<bits/stdc++.h>
+
+using namespace std;
+
+int main() {
+    int n; cin >> n;
+    vector<int> in(n);
+    for (auto &e: in) cin >> e;
+    int count = 1;
+    map<int, int> pos;
+    for (int i{}; i < n; i++) pos[in[i]] = i;
+    for (int i = 1; i < n; i++) {
+        if (pos[i] > pos[i+1]) count ++;
+    }
+    cout << count << endl;
+    return 0;
+}

CSES - CSES Problem Set/Collecting_Numbers_II.cpp

@@ -0,0 +1,39 @@
+//  Collecting Numbers II
+
+#include<bits/stdc++.h>
+
+using namespace std;
+
+int main() {
+    int n; cin >> n;
+    int m; cin >> m;
+    vector<int> in(n);
+    for (auto &e: in) cin >> e;
+    int count = 1;
+    unordered_map<int, int> pos;
+    for (int i{}; i < n; i++) pos[in[i]] = i;
+    for (int i = 1; i < n; i++) {
+        if (pos[i] > pos[i+1]) count ++;
+    }
+//    cout << count << endl;
+    for (int i{}; i < m; i++) {
+        int a, b; cin >> a >> b;
+
+
+        if (in[a - 1] > 1 && pos[in[a - 1] - 1] > a - 1 && pos[in[a - 1] - 1] <= b - 1) count--;
+        if (in[a - 1] > 1 && pos[in[a - 1] - 1] < a - 1 && pos[in[a - 1] - 1] >= b - 1) count++;
+        if (in[a - 1] < n && pos[in[a - 1] + 1] > a - 1 && pos[in[a - 1] + 1] <= b - 1) count++; //
+        if (in[a - 1] < n && pos[in[a - 1] + 1] < a - 1 && pos[in[a - 1] + 1] >= b - 1) count--;
+
+        if (in[b - 1] > 1 && pos[in[b - 1] - 1] > a - 1 && pos[in[b - 1] - 1] < b - 1) count++;
+        if (in[b - 1] > 1 && pos[in[b - 1] - 1] < a - 1 && pos[in[b - 1] - 1] > b - 1) count--;
+        if (in[b - 1] < n && pos[in[b - 1] + 1] > a - 1 && pos[in[b - 1] + 1] < b - 1) count--;
+        if (in[b - 1] < n && pos[in[b - 1] + 1] < a - 1 && pos[in[b - 1] + 1] > b - 1) count++;
+
+        pos[in[a - 1]] = b - 1;
+        pos[in[b - 1]] = a - 1;
+        swap(in[a-1], in[b-1]);
+        cout << count << endl;
+    }
+    return 0;
+}

CSES - CSES Problem Set/Missing_Coin_Sum.cpp

@@ -0,0 +1,27 @@
+//  Missing Coin Sum
+
+#include<bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+int main() {
+    int n; cin >> n;
+    vector<ll> coins(n);
+    for (auto &e: coins) cin >> e;
+    std::sort(coins.begin(), coins.end());
+
+    ll sum = 0;
+
+    for (int i{}; i < n; i++) {
+        if (coins[i] - 1 > sum) {
+            break;
+        } else {
+            sum += coins[i];
+        }
+    }
+
+    cout << sum + 1 << endl;
+
+    return 0;
+}

CSES - CSES Problem Set/Stick_Lengths.cpp

@@ -0,0 +1,24 @@
+//  Stick Lengths
+
+#include<bits/stdc++.h>
+
+using namespace std;
+using ll = long long;
+
+int main() {
+    int n; cin >> n;
+    vector<ll> in(n);
+    for (auto &e: in) cin >> e;
+    std::sort(in.begin(), in.end());
+    ll target = in[n/2];
+    ll target2 = in[n/2 + 1];
+    ll count = 0, count2 = 0;
+    for (auto e: in) {
+        count += abs(target - e);
+        count2 += abs(target2 - e);
+    }
+    cout << min(count, count2) << endl;
+
+
+    return 0;
+}