KGSS segment tree node

KGSS segment tree node.cpp

struct SegmentTreeNode {
  int maxNum, secondMaxNum;
  
  void assignLeaf(int num) {
    maxNum = num;
    secondMaxNum = -1;
  }
  
  void merge(SegmentTreeNode& left, SegmentTreeNode& right) {
    maxNum = max(left.maxNum, right.maxNum);
    secondMaxNum = min(max(left.maxNum, right.secondMaxNum), max(right.maxNum, left.secondMaxNum));
  }
  
  int getValue() {
    return maxNum + secondMaxNum;
  }
};