problems(cpp): add “1146. Snapshot Array”

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/cpp/snapshot-array.cpp

@@ -0,0 +1,63 @@
+#include <algorithm>
+#include <cassert>
+#include <map>
+#include <vector>
+
+class SnapshotArray {
+    int snap_id = 0;
+    std::vector<std::map<int, int>> arr;
+
+public:
+    SnapshotArray(int length)
+        : arr(length, std::map<int, int> { { 0, 0 } })
+    {
+    }
+
+    void set(int index, int val)
+    {
+        arr[index][snap_id] = val;
+    }
+
+    int snap()
+    {
+        return snap_id++;
+    }
+
+    int get(int index, int snap_id)
+    {
+        auto it = std::prev(arr[index].lower_bound(snap_id + 1));
+        return it == arr[index].end() ? 0 : it->second;
+    }
+};
+
+/**
+ * Your SnapshotArray object will be instantiated and called as such:
+ * SnapshotArray* obj = new SnapshotArray(length);
+ * obj->set(index,val);
+ * int param_2 = obj->snap();
+ * int param_3 = obj->get(index,snap_id);
+ */
+
+int main()
+{
+    SnapshotArray arr(3);
+    arr.set(0, 5);
+    assert(arr.snap() == 0);
+
+    arr.set(0, 6);
+    assert(arr.get(0, 0) == 5);
+    assert(arr.get(0, 1) == 6);
+
+    arr = SnapshotArray(1);
+    arr.set(0, 15);
+
+    assert(arr.snap() == 0);
+    assert(arr.snap() == 1);
+    assert(arr.snap() == 2);
+    assert(arr.get(0, 2) == 15);
+    assert(arr.snap() == 3);
+    assert(arr.snap() == 4);
+    assert(arr.get(0, 0) == 15);
+
+    return 0;
+}