O(nlong)

Author: skjha1

Diff for: src/Algorithms/Divide & Conquer/03 Merge sort.cpp

@@ -0,0 +1,50 @@
+class Solution {
+public:
+   void merge(vector<int>& nums, int l, int m, int r)
+{
+    int n1 = m - l + 1;
+    int n2 = r - m;
+    int A[n1], B[n2];
+    
+    for(int i = 0; i < n1; i++)
+        A[i] = nums[l + i];
+    
+    for(int i = 0; i < n2; i++)
+        B[i] = nums[m + 1 + i];
+    
+    int i = 0, j = 0;
+    int k = l;
+    
+    while(i < n1 && j < n2)
+    {
+        if(A[i] <= B[j])
+            nums[k++] = A[i++];
+        else
+            nums[k++] = B[j++];
+    }
+    
+    while(i < n1)
+        nums[k++] = A[i++];
+    while(j < n2)
+        nums[k++] = B[j++];
+}
+
+void mergeSort(vector<int>& nums, int l, int r)
+{
+    if(l >= r)  //remember to put the equal to sign
+        return;
+    
+    int m = l + (r - l)/2;
+    mergeSort(nums, l, m);
+    mergeSort(nums, m + 1, r);
+    merge(nums, l, m, r);
+}
+
+vector<int> sortArray(vector<int>& nums) 
+{
+    mergeSort(nums, 0, nums.size() - 1);
+    return nums;
+}  
+        
+    
+};