bool VerifySquenceOfBST(int sequence[], int length)
{
if(sequence == NULL || length <= 0)
return false;
int root = sequence[length - 1];
// nodes in left sub-tree are less than root node
int i = 0;
for(; i < length - 1; ++ i)
{
if(sequence[i] > root)
break;
}
// nodes in right sub-tree are greater than root node
int j = i;
for(; j < length - 1; ++ j)
{
if(sequence[j] < root)
return false;
}
// Is left sub-tree a binary search tree?
bool left = true;
if(i > 0)
left = VerifySquenceOfBST(sequence, i);
// Is right sub-tree a binary search tree?
bool right = true;
if(i < length - 1)
right = VerifySquenceOfBST(sequence + i, length - i - 1);
return (left && right);
}
bool VerifySquenceOfBST(vector<int> sequence)
{
if(sequence.empty())
{
return true;
}
vector<int>::iterator root = sequence.end();
root--;
vector<int>::iterator flag1 = sequence.begin() , flag;
while((*flag1) < (*root))
flag1++;
flag = flag1;
while(flag1 != root)
{
if(*flag1 < *root)
return false;
flag1++;
}
vector<int> left(sequence.begin(), flag);
vector<int> right(flag, root);
return VerifySquenceOfBST(left) && VerifySquenceOfBST(right);
}
// ==================== Test Code ====================
void Test(char* testName, int sequence[], int length, bool expected)
{
if(testName != NULL)
printf("%s begins: ", testName);
if(VerifySquenceOfBST(sequence, length) == expected)
printf("passed.\n");
else
printf("failed.\n");
}