diff --git a/data_structure/disjoint_set.cpp b/data_structure/disjoint_set.cpp
index de5d1c0e0..71b220ab9 100644
--- a/data_structure/disjoint_set.cpp
+++ b/data_structure/disjoint_set.cpp
@@ -1,69 +1,64 @@
 #include <iostream>
 #include <vector>
-using namespace std;
+
+using std::cout;
+using std::endl;
+using std::vector;
 
 vector<int> root, rnk;
 
-void CreateSet(int n){
-    root = vector<int> (n+1);
-    rnk = vector<int> (n+1, 1);
-    
-    for(int i = 1; i <= n; ++ i) {
-        root[i] = i;
-    }
+void CreateSet(int n) {
+  root = vector<int> (n+1);
+  rnk = vector<int> (n+1, 1);
+  for (int i = 1; i <= n; ++i) {
+    root[i] = i;
+  }
 }
 
 int Find(int x) {
-    if (root[x] == x) {
-        return x;
-    }
-    return root[x] = Find(root[x]);
+  if (root[x] == x) {
+    return x;
+  }
+  return root[x] = Find(root[x]);
 }
 
 bool InSameUnion(int x, int y) {
-    return Find(x) == Find(y);
+  return Find(x) == Find(y);
 }
 
 void Union(int x, int y) {
-    int a = Find(x), b = Find(y);
-    if(a != b) {
-        if (rnk[a] < rnk[b]) {
-            root[a] = b;
-        } else if (rnk[a] > rnk[b]) {
-            root[b] = a;
-        } else {
-            root[a] = b;
-            ++ rnk[b];
-        }
+  int a = Find(x), b = Find(y);
+  if (a != b) {
+    if (rnk[a] < rnk[b]) {
+      root[a] = b;
+    } else if (rnk[a] > rnk[b]) {
+      root[b] = a;
+    } else {
+      root[a] = b;
+      ++rnk[b];
     }
+  }
 }
 
 int main() {
-    
-    // tests CreateSet & Find
-    
-    int n = 100;
-    CreateSet(n);
-    
-    for (int i = 1; i <= 100; ++ i) {
-        if (root[i] != i) {
-            cout << "Fail" << endl;
-            break;
-        }
+  // tests CreateSet & Find
+  int n = 100;
+  CreateSet(n);
+  for (int i = 1; i <= 100; ++i) {
+    if (root[i] != i) {
+      cout << "Fail" << endl;
+      break;
     }
-    
-    // tests InSameUnion & Union
-    
-    cout << "1 and 2 are initially not in the same subset" << endl;
-    if (InSameUnion(1, 2)) {
-        cout << "Fail" << endl;
-    }
-        
-    Union(1, 2);
-    cout << "1 and 2 are now in the same subset" << endl;
-    if (!InSameUnion(1, 2)) {
-        cout << "Fail" << endl;
-    }
-    
-    return 0;
+  }
+  // tests InSameUnion & Union
+  cout << "1 and 2 are initially not in the same subset" << endl;
+  if (InSameUnion(1, 2)) {
+    cout << "Fail" << endl;
+  }
+  Union(1, 2);
+  cout << "1 and 2 are now in the same subset" << endl;
+  if (!InSameUnion(1, 2)) {
+    cout << "Fail" << endl;
+  }
+  return 0;
 }