MS100(9)-判断整数序列是不是二元查找树的后序遍历结果

#include <iostream>

using namespace std;

 

bool verifySquenceOfBST(int squence[], int length)

{

    if(squence == NULL || length <= 0)

        return false;

    // root of a BST is at the end of post order traversal squence

    int root = squence[length - 1];

    // the nodes in left sub-tree are less than the root

    int i = 0;

    for(; i < length - 1; ++ i)

    {

        if(squence[i] > root)

            break;

    }

    // the nodes in the right sub-tree are greater than the root

    int j = i;

    for(; j < length - 1; ++ j)

    {

        if(squence[j] < root)

            return false;

    }

    // verify whether the left sub-tree is a BST

    bool left = true;

    if(i > 0)

        left = verifySquenceOfBST(squence, i);

    // verify whether the right sub-tree is a BST

    bool right = true;

    if(i < length - 1)

        right = verifySquenceOfBST(squence + i, length - i - 1);

    return (left && right);

}

 

int main(void)

{

    int len,s[100];

    while (cin>>len)

    {

        for(int i=0;i<len;i++)

            cin>>s[i];

        if(verifySquenceOfBST(s,len))

            cout<<"ok!"<<endl;

        else

            cout<<"false!"<<endl;

    }

    return 0;

}