https://github.com/ndesai15/coding-java/blob/master/src/com/coding/patterns/stacks/MinStack.java

Bug:
public void push(int val) {
stack.push(val);
if (minStack.isEmpty() || val <= minStack.peek()) {
minStack.push(val);
}
}

Fix:
public void push(int val) {
stack.push(val);
if(minstack.isEmpty()||val<minstack.peek()){
minstack.push(val);
}
else{
minstack.push(minstack.peek());
}
}

Open to suggestions!

How can we start including System Design Questions in Code repository itself?

https://github.com/ndesai15/coding-java/blob/master/src/com/coding/patterns/topologicalsort/AlienDictionary.java

In line 7

If words is really null, then words.length will throw NullPointerException first before checking whether it is null or not.

So either we assume all given words is non-null or we change the order like if (words == null || words.length ...)

Currently Answer will fail with below test case:

[805306368,805306368,805306368]
1000000000

I think we need to change count method return type from int to long to make it work.

  private long count(int[] piles, int k) {
        long result = 0;
        for(int pile : piles) {
            result += (pile / k) + (pile % k == 0 ? 0 : 1);
        }
        return result;
    }

Looking for a contributor to update/add more already implemented problem references in README

Hi,

I noticed that the coin change answer is incorrect: https://github.com/ndesai15/coding-java/blob/master/src/com/coding/patterns/dynamicprogramming/knapsack/unbounded/CoinChange.java. The example coins = [2], amount = 3 should result in -1. This code would return 4.

Leetcode issue: https://leetcode.com/problems/coin-change/

Solution code here returns Runtime Error when submitting.
java.util.EmptyStackException
at line 101, java.base/java.util.Stack.peek
at line 27, MinStack.getMin
at line 72, Driver.helperSelectMethod
at line 90, Driver.helper
at line 111, Driver.main

Below code resolves the issue:
class MinStack {

private Stack<int[]> stack = new Stack<>();

public MinStack() {
}

public void push(int val) {
    
    if (stack.isEmpty()) {
        stack.push(new int[]{val, val});
        return;
    }
    int currentMin = stack.peek()[1];
    stack.push(new int[]{val, Math.min(val, currentMin)});
}

public void pop() {
    stack.pop();
}

public int top() {
    return stack.peek()[0];
}

public int getMin() {
    return stack.peek()[1];
}

}

https://github.com/ndesai15/coding-java/blob/master/src/com/coding/patterns/tree/BalancedBinaryTree.java

The isBalance method in the linked solution does not work (the method should be called isBalanced).

SearchInRotatedSortedArray.java fails for data:

int result = searchInRotatedSortedArray.search( new int[] { 5, 1, 3 }, 2 );
Assert.assertEquals( result, -1 );

It does not return and times out

Code on line 30:

 left = mid - 1;

should be changed to

 left = mid + 1;

Hello,

Looking for a contributor to contribute to com.companies package. Intention of this package to include most frequently asked questions in companies like FAANG or any other company that can help others. Feel free to contribute to this package by creating a package on a name of company & include code implementation.

Looking for a simple CI process to validate source code on every merge to master. So that we don't include any buggy code to repository.

I do not have premium access to AlienDictonary on leetcode. I think this solution is for leetcode.

The wording of the question on lintcode is different to the wording of the question on leetcode (I think).

The lintcode wording on https://www.lintcode.com/problem/892/ includes:

  "There may be multiple valid order of letters, return the smallest in normal lexicographical order."

The Java AlienDictionary solution does not cater for this.

The code looks like:

StringBuilder sortedOrder = new StringBuilder();

while (!sources.isEmpty()) {
        Character vertex = sources.remove();
        sortedOrder.append(vertex);
        for (char c: graph.get(vertex)) {
            inDegree.put(c, inDegree.get(c) - 1);
            if (inDegree.get(c) == 0) {
                sources.add(c);
            }
        }
    }

Notice there is no sorting going on with the StringBuilder

I think that the main problem you have is that on:

 needcode.io blind75 Advanced Graph - Alien Dictionary

the Alien Dictionary link goes to:

 https://www.lintcode.com/problem/892/

while the Java Solution is for leetcode which is locked and is only available for premium members.

I think it will help others if this is somehow conveyed to the readers of needcode.io, blind75, Advanced Graph - Alien Dictionary

Thank you