diff --git a/src/main/java/com/dota/bit/_2154/Solution.java b/src/main/java/com/dota/bit/_2154/Solution.java
new file mode 100644
index 0000000..b41b12e
--- /dev/null
+++ b/src/main/java/com/dota/bit/_2154/Solution.java
@@ -0,0 +1,16 @@
+package com.dota.bit._2154;
+
+class Solution {
+
+    public int findFinalValue(int[] nums, int original) {
+        var dp = new int[1001];
+        for (int num : nums) {
+            dp[num]++;
+        }
+        while(dp[original] > 0) {
+            original <<=1;
+        }
+        return original;
+    }
+
+}
\ No newline at end of file
diff --git a/src/main/java/com/dota/bit/_2220/Solution.java b/src/main/java/com/dota/bit/_2220/Solution.java
new file mode 100644
index 0000000..1b9e1ca
--- /dev/null
+++ b/src/main/java/com/dota/bit/_2220/Solution.java
@@ -0,0 +1,7 @@
+package com.dota.bit._2220;
+
+class Solution {
+    public int minBitFlips(int start, int goal) {
+        return Integer.bitCount(start ^ goal);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/dota/bit/_2595/Solution.java b/src/main/java/com/dota/bit/_2595/Solution.java
new file mode 100644
index 0000000..0ceb976
--- /dev/null
+++ b/src/main/java/com/dota/bit/_2595/Solution.java
@@ -0,0 +1,8 @@
+package com.dota.bit._2595;
+
+class Solution {
+	public int[] evenOddBit(int n) {
+		int a = 0x555555;
+		return new int[]{Integer.bitCount(n&a), Integer.bitCount(n&(~a))};
+	}
+}
\ No newline at end of file
diff --git a/src/main/java/com/dota/bit/_2657/Solution.java b/src/main/java/com/dota/bit/_2657/Solution.java
new file mode 100644
index 0000000..b2665e2
--- /dev/null
+++ b/src/main/java/com/dota/bit/_2657/Solution.java
@@ -0,0 +1,29 @@
+package com.dota.bit._2657;
+
+class Solution {
+	public int[] findThePrefixCommonArray(int[] A, int[] B) {
+		var dp = new int[51];
+		var res = new int[A.length];
+		int cnt = 0;
+		for (int i = 0; i < A.length; i++) {
+			if (A[i] == B[i]) {
+				cnt++;
+			} else {
+				if (dp[A[i]] != 0) {
+					cnt++;
+				} else {
+					dp[A[i]]++;
+				}
+
+				if (dp[B[i]] != 0) {
+					cnt++;
+				} else {
+					dp[B[i]]++;
+				}
+			}
+
+			res[i] = cnt;
+		}
+		return res;
+	}
+}
\ No newline at end of file
diff --git a/src/main/java/com/dota/bit/_2917/Solution.java b/src/main/java/com/dota/bit/_2917/Solution.java
new file mode 100644
index 0000000..bd4b3ae
--- /dev/null
+++ b/src/main/java/com/dota/bit/_2917/Solution.java
@@ -0,0 +1,17 @@
+package com.dota.bit._2917;
+
+class Solution {
+	public int findKOr(int[] nums, int k) {
+		int res = 0;
+		for (int i = 0; i < 31; i++) {
+			int count = 0;
+			for (int num : nums) {
+				count += (num >> i) & 1;
+			}
+			if (count >= k) {
+				res |= (1<<i);
+			}
+		}
+		return res;
+	}
+}
\ No newline at end of file
diff --git a/src/main/java/com/dota/bit/_3211/Solution.java b/src/main/java/com/dota/bit/_3211/Solution.java
new file mode 100644
index 0000000..628378f
--- /dev/null
+++ b/src/main/java/com/dota/bit/_3211/Solution.java
@@ -0,0 +1,31 @@
+package com.dota.bit._3211;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+class Solution {
+	public List<String> validStrings(int n) {
+		var res = new HashSet<String>();
+		StringBuilder sb = new StringBuilder();
+		sb.append("1".repeat(n));
+		df(sb, res, 0, "0");
+		df(sb, res, 0, "1");
+		return new ArrayList<>(res);
+	}
+
+	void df(StringBuilder sb, Set<String> list, int idx, String s) {
+		if (idx >= sb.length()) return;
+		char c = sb.charAt(idx);
+		sb.replace(idx, idx + 1, s);
+		list.add(sb.toString());
+		if (s.equals("0")) {
+			df(sb, list, idx + 1, "1");
+		} else {
+			df(sb, list, idx + 1, "0");
+			df(sb, list, idx + 1, "1");
+		}
+		sb.setCharAt(idx, c);
+	}
+}
\ No newline at end of file
diff --git a/src/main/java/com/dota/bit/_3226/Solution.java b/src/main/java/com/dota/bit/_3226/Solution.java
new file mode 100644
index 0000000..2e48331
--- /dev/null
+++ b/src/main/java/com/dota/bit/_3226/Solution.java
@@ -0,0 +1,9 @@
+package com.dota.bit._3226;
+
+class Solution {
+    public int minChanges(int n, int k) {
+        if (n != (n | k)) return -1;
+
+        return Integer.bitCount(n ^ k);
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/com/dota/bit/_3370/Solution.java b/src/main/java/com/dota/bit/_3370/Solution.java
new file mode 100644
index 0000000..20d6b42
--- /dev/null
+++ b/src/main/java/com/dota/bit/_3370/Solution.java
@@ -0,0 +1,12 @@
+package com.dota.bit._3370;
+
+class Solution {
+	public int smallestNumber(int n) {
+		int res = 1;
+		while (n > res) {
+			res <<=1;
+			res += 1;
+		}
+		return res;
+	}
+}
\ No newline at end of file