《编程之美: 求二叉树中节点的最大距离》的另一个解法

#include <iostream>

using namespace std;

struct NODE
{
NODE *pLeft;
NODE *pRight;
};

struct RESULT
{
int nMaxDistance;
int nMaxDepth;
};

RESULT GetMaximumDistance(NODE* root)
{
if (!root)
{
RESULT empty = { 0, -1 };   // trick: nMaxDepth is -1 and then caller will plus 1 to balance it as zero.
return empty;
}

RESULT lhs = GetMaximumDistance(root->pLeft);
RESULT rhs = GetMaximumDistance(root->pRight);

RESULT result;
result.nMaxDepth = max(lhs.nMaxDepth + 1, rhs.nMaxDepth + 1);
result.nMaxDistance = max(max(lhs.nMaxDistance, rhs.nMaxDistance), lhs.nMaxDepth + rhs.nMaxDepth + 2);
return result;
}