Kth Largest Element in an Array

Kth Largest Element in an Array.cpp

@@ -0,0 +1,89 @@
+
+    int findKthLargest(vector<int>& nums, int k) 
+    {
+        if( k == 1 )
+        {
+            int mv = INT_MIN;
+            for( size_t i = 0; i < nums.size(); ++i)          
+                mv = std::max(mv,nums[i]);
+
+            return mv;        
+        }
+        else
+        {
+            vector<int> heap;
+            for( size_t i = 0; i < nums.size(); ++i)
+                pushHeap(heap, k, nums[i]);
+
+            return heap[0];       
+        }
+    }
+
+    void pushHeap(vector<int>& heap, int k, int v)
+    {
+        // cout << "Push: " << v << endl;
+
+        if( heap.size() == (size_t)k )
+        {
+            if( v <= heap[0] ) 
+                return; 
+
+            //Adjust Heap
+            heap[0] = v;
+            adjustHeap(heap, k, 0 );
+        }
+        else
+        {
+            heap.push_back(v);
+
+            // Build Heap
+            if( heap.size() == (size_t)k )
+            {
+                for(int pos = k/2-1; pos >= 0; --pos)
+                {
+                    int posL = 2*pos+1;
+                    int posR = posL+1;
+
+                    if( heap[posL] < heap[pos] )
+                    {
+                        swap( heap, posL, pos);
+                        adjustHeap(heap, k , posL);
+                    }
+
+                    if(posR < k && heap[posR] < heap[pos] )
+                    {
+                        swap( heap, posR, pos);
+                        adjustHeap(heap, k , posR);
+                    }
+                }
+
+                // cout << "Build: " << heap << endl;
+            }
+        }
+    }
+
+    void adjustHeap(vector<int>& heap, int k, int pos)
+    {
+        while (pos <= (k/2-1))
+        {
+            int child = 2*pos+1; 
+
+            if( (child + 1) < k && heap[child] > heap[child+1])
+                ++child;
+
+            if( heap[pos] <= heap[child])
+                break;
+
+            swap( heap, pos, child);
+            pos = child;
+        }
+
+        // cout << "Adjust: " << heap << endl;
+    }
+
+    void swap(vector<int>& heap, int a, int b)
+    {
+        int t = heap[a];
+        heap[a] = heap[b];
+        heap[b] = t;
+    }