diff --git a/80-231129/main.cpp b/80-231129/main.cpp
new file mode 100644
index 0000000..330d083
--- /dev/null
+++ b/80-231129/main.cpp
@@ -0,0 +1,59 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+class Solution {
+public:
+    int removeDuplicates(vector<int>& nums) {
+        const int number_limit = 2*1e4+10;
+        int numbers[number_limit] = {};
+        const int shift = 1e4;
+        for(int i = 0 ; i < nums.size() ; i++){
+            numbers[nums[i]+shift]++;
+        }
+        int sum = 0;
+        int cur = 0;
+        for(int i = 0 ; i < number_limit ;i++){
+            if(numbers[i]>=2){
+                nums[cur++] = i-shift;
+                nums[cur++] = i-shift;
+                sum += 2;
+            }else if(numbers[i] == 1){
+                nums[cur++] = i-shift;
+                sum += 1;
+            }
+        }
+        return sum;
+    }
+    int better(vector<int>& nums){
+        int i = 0 ; 
+        for(int ele: nums){
+            if( i==0 || i==1 || nums[i-2]!=ele){
+                nums[i] = ele;
+                i++;
+            }
+        }
+        return i;
+    }
+};
+
+int main(){
+
+    Solution sol;
+    vector<int> ex1 = {1,1,1,2,2,3};
+    // int k = sol.removeDuplicates(ex1);
+    int k = sol.better(ex1);
+    cout<<k<<endl;
+    for(int i = 0 ; i < k ; i++){
+        cout<<ex1[i]<<' ';
+    }
+    cout<<endl;
+    vector<int> ex2 = {0,0,1,1,1,1,2,3,3};
+    // k = sol.removeDuplicates(ex2);
+    k = sol.better(ex2);
+    cout<<k<<endl;
+    for(int i = 0 ; i < k ; i++){
+        cout<<ex2[i]<<' ';
+    }
+    cout<<endl;
+    return 0;
+}
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