[Algorithm] How to use Max Heap to maintain K smallest items

Let's say we are given an array:

[,,,,,,]

We want to get K = 3 smallest items from the array and using Max heap data structure.

So this is how to think about it.

1. We take first K items put it into Max Heap:

5

/     \

4          1

2. Then we move forward to next element '2' in the array, we check

• Whether 2 is smaller than current max item in heap, which is '5', if yes, then replace 5 with 2
• Then re-arrange the heap

4

/    \

2         1

3. Repeat the process for items [3,0]

3　　　　　　　　2

/    \                   /　　\

2         1              0　　　　1

4. When the item is '10' which is larger than current max '2', we just ingore it.

5. In the end, we got K smallest items, we just need to print it out. (K smallest items are not ncessary in order)