merge k-way sorted array

Author: xiaoningning

PuzzleCoding/src/MergeSortedArray.java

@@ -35,13 +35,18 @@ public MinHeapArrayNode() {
         }
 
         public void insert(ArrayNode node) {
+            if(node == null)
+                throw new RuntimeException("can't insert null node");
+
             heap.add(node);
             shiftUp(heap.size() - 1);
         }
 
         public ArrayNode removeMin() {
             if (isEmpty())
                 throw new RuntimeException("heap is empty");
+
+            System.out.println(heap.toString());
             ArrayNode min = heap.get(1);
             heap.remove(min);
 
@@ -63,7 +68,7 @@ private void shiftDown(int k) {
             while (2 * k <= heap.size() - 1) {
                 int i = 2 * k; //left
                 int j = i + 1; //right
-                if (i < heap.size() - 1 && greater(j, i)) {
+                if (i < heap.size() - 1 && greater(i, j)) {
                     i++;
                 }
                 if (greater(i, k)) break;
@@ -97,7 +102,8 @@ public static void main(String[] args) {
         Integer[][] arrays = new Integer[][]{
                 {1, 5, 9},
                 {4, 8, 10},
-                {6, 11}
+                {6, 11},
+                {2,7}
         };
 
         ArrayList<Integer> result = mergeSortedArray(arrays);

PuzzleCoding/src/MinHeap.java

@@ -98,7 +98,7 @@ public void printHeap() {
     }
 
     public static void main(String[] args) {
-        int[] a = new int[]{5, 3, 1, 0, 6, 7, 2};
+        int[] a = new int[]{5, 3, 4, 1, 0, 6, 7, 2};
         MinHeap minHeap = new MinHeap(a.length);
         for (int i = 0; i < a.length; i++) {
             minHeap.insert(a[i]);