diff --git a/src/problem/mod.rs b/src/problem/mod.rs
index 2733115..06b3074 100644
--- a/src/problem/mod.rs
+++ b/src/problem/mod.rs
@@ -186,4 +186,5 @@ mod p295_find_median_from_data_stream;
 mod p67_add_binary;
 mod p190_reverse_bits;
 mod p191_number_of_1_bits;
-mod p136_single_number;
\ No newline at end of file
+mod p136_single_number;
+mod p137_single_number_ii;
\ No newline at end of file
diff --git a/src/problem/p137_single_number_ii.rs b/src/problem/p137_single_number_ii.rs
new file mode 100644
index 0000000..859fe98
--- /dev/null
+++ b/src/problem/p137_single_number_ii.rs
@@ -0,0 +1,32 @@
+/**
+ * [137] Single Number II
+ */
+pub struct Solution {}
+
+
+// submission codes start here
+
+impl Solution {
+    pub fn single_number(nums: Vec<i32>) -> i32 {
+        let (mut a, mut b)  = (0, 0);
+        
+        for i in nums {
+            b = !a & (b ^ i);
+            a = !b & ( a ^ i);
+        }
+        
+        b
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_137() {
+        assert_eq!(1, Solution::single_number(vec![1, 2, 2, 2]));
+    }
+}