diff --git a/.idea/misc.xml b/.idea/misc.xml
index fdc35ea..512b2e9 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -8,7 +8,5 @@
       </list>
     </option>
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="21" project-jdk-type="JavaSDK">
-    <output url="file://$PROJECT_DIR$/out" />
-  </component>
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="graalvm-21" project-jdk-type="JavaSDK" />
 </project>
\ No newline at end of file
diff --git a/.idea/vcs.xml b/.idea/vcs.xml
index 94a25f7..35eb1dd 100644
--- a/.idea/vcs.xml
+++ b/.idea/vcs.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
   <component name="VcsDirectoryMappings">
-    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+    <mapping directory="" vcs="Git" />
   </component>
 </project>
\ No newline at end of file
diff --git a/src/main/java/com/dota/binarySearch/_1146/SnapshotArray.java b/src/main/java/com/dota/binarySearch/_1146/SnapshotArray.java
new file mode 100644
index 0000000..e4e6ee6
--- /dev/null
+++ b/src/main/java/com/dota/binarySearch/_1146/SnapshotArray.java
@@ -0,0 +1,29 @@
+package com.dota.binarySearch._1146;
+
+import java.util.TreeMap;
+
+class SnapshotArray {
+    int cnt = 0;
+    TreeMap<Integer, Integer>[] arr ;
+    int n;
+    public SnapshotArray(int length) {
+        arr = new TreeMap[length];
+        n = length;
+        for (int i = 0; i < n; i++) {
+            arr[i] = new TreeMap<>();
+            arr[i].put(0, 0);
+        }
+    }
+    
+    public void set(int index, int val) {
+        arr[index].put(cnt, val);
+    }
+    
+    public int snap() {
+        return cnt++;
+    }
+    
+    public int get(int index, int snap_id) {
+        return  arr[index].floorEntry(snap_id).getValue();
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/dota/binarySearch/_981/TimeMap.java b/src/main/java/com/dota/binarySearch/_981/TimeMap.java
new file mode 100644
index 0000000..be3a338
--- /dev/null
+++ b/src/main/java/com/dota/binarySearch/_981/TimeMap.java
@@ -0,0 +1,43 @@
+package com.dota.binarySearch._981;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+class TimeMap {
+    Map<String, List<String>> vmap;
+    Map<String, List<Integer>> imap;
+    public TimeMap() {
+        vmap = new HashMap<>();
+        imap = new HashMap<>();
+    }
+
+    public void set(String key, String value, int timestamp) {
+        vmap.computeIfAbsent(key, k -> new ArrayList<>()).add(value);
+        imap.computeIfAbsent(key, k -> new ArrayList<>()).add(timestamp);
+    }
+
+    public String get(String key, int timestamp) {
+        var vList = vmap.get(key);
+        var iList = imap.get(key);
+        if (vList == null || iList == null) return "";
+        int l= 0, r = iList.size()-1;
+        while (l <= r) {
+            int mid = l + (r - l) / 2;
+            if (iList.get(mid)==timestamp) {
+                return vList.get(mid);
+            }
+            if (iList.get(mid)>timestamp) {
+                r = mid - 1;
+            } else {
+                l = mid + 1;
+            }
+        }
+        if (r < 0) {
+            return "";
+        }
+        return vList.get(r);
+    }
+}
+    
\ No newline at end of file