Create Sort by Set Bit Count

Sort by Set Bit Count

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+// { Driver Code Starts
+#include <bits/stdc++.h>
+using namespace std;
+
+
+ // } Driver Code Ends
+
+This question is now solved.......................
+/*
+bool compare(int a,int b){
+    int ca=0,cb=0;
+    while(a){
+        if(a&1)ca++;
+        a=a>>1;
+    }
+    while(b){
+        if(b&1)cb++;
+        b=b>>1;
+    }
+    return ca>cb;
+}
+*/
+int countBits(int a)
+{
+    int count = 0;
+    while (a) {
+        if (a & 1)
+            count += 1;
+        a = a >> 1;
+    }
+    return count;
+}
+
+// custom comparator of std::sort
+int cmp(int a, int b)
+{
+    int count1 = countBits(a);
+    int count2 = countBits(b);
+
+    // this takes care of the stability of
+    // sorting algorithm too
+    if (count1 <= count2)
+        return false;
+    return true;
+}
+class Solution{
+    public:
+    void sortBySetBitCount(int arr[], int n)
+    {
+        // Your code goes here
+        stable_sort(arr,arr+n,cmp);
+    }
+};
+
+// { Driver Code Starts.
+
+int main()
+{
+    int t;
+    cin>>t;
+    while(t--){
+        int n;
+        cin>>n;
+        int arr[n];
+        for(int i=0;i<n;i++){
+            cin>>arr[i];
+        }
+        Solution ob;
+        ob.sortBySetBitCount(arr, n);
+        for (int i = 0; i < n; i++)
+            cout << arr[i] << " ";
+        cout << endl;
+    }
+    return 0;
+}
+  // } Driver Code Ends