EarliestMonth

a prefix sum problem - store prefix sum for each index and then check for left i and right n-i elements difference.

public static void main(String[] args){
    MinNetPrice minNetPrice = new MinNetPrice();
    System.out.println(minNetPrice.minNetPrice(new int[]{1,3,2,3}));
}
public int minNetPrice(int[] stockPrice){
    int sum = 0;
    for(int i : stockPrice){
        sum+=i;
    }
    int minNetPrice = Integer.MAX_VALUE, month=-1, n = stockPrice.length;
    int leftSum=0,rightSum = sum;
    for(int i=1;i<n;i++){
       leftSum+=stockPrice[i-1];
       rightSum-=stockPrice[i-1];
       int currNet = Math.abs((leftSum/i)-(rightSum/(n-i)));
       if(minNetPrice>currNet){
           minNetPrice = currNet;
           month = i;
           if(minNetPrice==0) break;
       }
    }
    return month;
}