Given an Array of Integers find the maximum product of increasing subsequence of size 3 . If a valid subsequence cannot be formed print -1

Answer:

Here's a code snippet for :Given an Array of Integers find the maximum product of increasing subsequence of size 3 . If a valid subsequence cannot be formed print -1

  static int maxProduct(int[]a){
    int n=a.length;
    int maxProduct=-1;
    int[]rightMax=new int[n];
    TreeSetset=new TreeSet<>();
    int maxRightElement=-1;
    for(int i=n-1;i>-1;i--){
      rightMax[i]=maxRightElement<a[i]?-1:maxRightElement;
      maxRightElement=Math.max(maxRightElement,a[i]);
    }
    for(int i=0;i<n;i++){
      if(set.lower(a[i])==null||rightMax[i]==-1)
      {         set.add(a[i]);
      continue;
      }
      maxProduct=Math.max(maxProduct,a[i]*set.lower(a[i])*rightMax[i]);
      set.add(a[i]);
    }
    return maxProduct;
  }