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/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;
+}