2024/11/21 灵茶题单 二分查找

src/main/java/com/cool/ling_cha_mount/binary_search/Num1146.java

@@ -0,0 +1,64 @@
+package com.cool.ling_cha_mount.binary_search;
+
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class Num1146 {
+
+
+    @Test
+    public void test() {
+        SnapshotArray snapshotArray = new SnapshotArray(4);
+        snapshotArray.snap();
+        snapshotArray.snap();
+        snapshotArray.get(3, 1);
+        snapshotArray.set(2, 4);
+        snapshotArray.snap();
+        snapshotArray.set(1, 4);
+    }
+}
+
+class SnapshotArray {
+
+    private int snap = 0;
+    private final Map<Integer, List<int[]>> map = new HashMap<>();
+
+    public SnapshotArray(int length) {
+    }
+
+    public void set(int index, int val) {
+        map.computeIfAbsent(index,key->new ArrayList<>()).add(new int[]{snap,val});
+    }
+
+    public int snap() {
+        return this.snap++;
+    }
+
+    public int get(int index, int snap_id) {
+        if(!map.containsKey(index)){
+            return 0;
+        }
+        List<int[]>list=map.get(index);
+        int i=binarySearch(list,snap_id);
+        return i>=0?list.get(i)[1]:0;
+    }
+
+    private int binarySearch(List<int[]>list,int target) {
+        int left=-1;
+        int right=list.size();
+        while(left+1<right){
+            int mid=(left+right)>>>1;
+            if(list.get(mid)[0]>target){
+                right=mid;
+            }else{
+                left=mid;
+            }
+        }
+        return left;
+    }
+}
+