LeastCommonAncestor.java

package Trees;

/**
 * Author - archit.s
 * Date - 09/11/18
 * Time - 4:34 PM
 */
public class LeastCommonAncestor {

    static boolean v1 = false, v2 = false;

    public TreeNode helper(TreeNode A, int B, int C){
        if(A == null){
            return null;
        }

        TreeNode t = null;

        if(A.val == B){
            v1 = true;
            t = A;
        }
        if(A.val == C){
            v2 = true;
            t = A;
        }

        TreeNode left = helper(A.left,B,C);
        TreeNode right = helper(A.right,B,C);

        if(t!=null){
            return t;
        }

        if(left!=null && right!=null){
            return A;
        }

        return (left!=null) ? left: right;
    }

    public int lca(TreeNode A, int B, int C) {

        v1 = false;
        v2 = false;

        TreeNode ans = helper(A,B,C);

        if(v1 && v2){
            return ans.val;
        }

        return -1;
    }
}