diff --git a/leet_1155.py b/leet_1155.py
new file mode 100644
index 0000000..7cb5854
--- /dev/null
+++ b/leet_1155.py
@@ -0,0 +1,42 @@
+class Solution:
+    def toHex(self, num: int) -> str:
+        mp = {}
+        for i in range(10):
+            mp[i] = str(i)
+        for i in range(10, 16):
+            mp[i] = chr(ord('a')+i-10)
+        
+        if num==0:
+            return str(0)
+        
+        ans = ""
+        neg = 1 if num < 0 else 0
+        
+        rev = {v:int(k) for k,v in mp.items()}
+        num = num*-1 if neg else num
+        while num:
+            dig = num%16
+            ans += mp[dig]
+            num//=16
+        ans = ans[::-1]
+        if neg:
+            mx = "ffffffff"
+            ans = ''.join(["0"]*(8-len(ans))) + ans
+            new_ans = ""
+            assert(len(ans) == len(mx))
+            for i in range(8):
+                new_ans += mp[rev[mx[i]] - rev[ans[i]]]
+            i=7
+            
+            print(new_ans, i)
+            f=0
+            while(i>0 and new_ans[i] == "f"):
+                new_ans = new_ans[:i] + "0" + new_ans[i+1:]
+                i-=1
+                f=1
+            new_ans = new_ans[:i] + mp[rev[new_ans[i]] + 1] + new_ans[i+1:]            
+            return new_ans
+                
+        else:
+            return ans
+            
diff --git a/leet_1310.py b/leet_1310.py
new file mode 100644
index 0000000..3f1d1fb
--- /dev/null
+++ b/leet_1310.py
@@ -0,0 +1,10 @@
+class Solution:
+    def xorQueries(self, arr: List[int], queries: List[List[int]]) -> List[int]:
+        pref = [0]
+        for e in arr:
+            pref.append(e ^ pref[-1])
+        ans = []
+        for [l, r] in queries:
+            ans.append(pref[r+1] ^ pref[l])
+        return ans
+        
diff --git a/leet_1525.py b/leet_1525.py
new file mode 100644
index 0000000..287d33d
--- /dev/null
+++ b/leet_1525.py
@@ -0,0 +1,16 @@
+import collections
+class Solution:
+    def numSplits(self, s: str) -> int:
+        lc, rc = collections.Counter(), collections.Counter(s)
+        
+        res = 0
+        for c in s:
+            lc[c] += 1
+            rc[c] -=1 
+            
+            if rc[c]==0:
+                del rc[c]
+            
+            if len(lc) == len(rc):
+                res +=1
+        return res
diff --git a/leet_338.cpp b/leet_338.cpp
new file mode 100644
index 0000000..79f1704
--- /dev/null
+++ b/leet_338.cpp
@@ -0,0 +1,28 @@
+class Solution {
+public:
+    vector<int> countBits(int num) {
+        vector<int> ans = {0, 1};
+        int n=2;
+        int tot = 2;
+        int j=0;
+        if(num==0){
+            vector<int> ans = {0};
+            return ans;
+        }
+        if(num==1){
+            vector<int> ans = {0, 1};
+            return ans;
+        }
+        
+        while(tot != num+1){
+            ans.push_back(ans[j]+1);
+            j+=1;
+            if(j==n){
+                j=0;
+                n*=2;
+            }
+            tot+=1;
+        }
+        return ans;
+    }
+};