added randomizedset

randomizedset/src/randomizedset.hpp

@@ -0,0 +1,38 @@
+#include <cstdlib>
+#include <ctime>
+#include <unordered_map>
+#include <vector>
+
+class RandomizedSet {
+ public:
+  RandomizedSet() {
+    srand(time(nullptr));
+  }
+
+  bool insert(int val) {
+    if (map.find(val) != map.end()) return false;
+    map[val] = list.size();
+    list.push_back(val);
+    return true;
+  }
+
+  bool remove(int val) {
+    auto it = map.find(val);
+    if (it == map.end()) return false;
+    int idx = it->second;
+    int lastVal = list.back();
+    list[idx] = lastVal;
+    map[lastVal] = idx;
+    list.pop_back();
+    map.erase(it);
+    return true;
+  }
+
+  int getRandom() {
+    return list[rand() % list.size()];
+  }
+
+ private:
+  std::vector<int> list;
+  std::unordered_map<int, int> map;
+};