统计前面比自己小的数的个数-LintCode

给定一个整数数组（下标由 0 到 n-1， n 表示数组的规模，取值范围由 0 到10000）。对于数组中的每个 ai 元素，请计算 ai 前的数中比它小的元素的数量。

注意事项：
We suggest you finish problem Segment Tree Build, Segment Tree Query II and Count of Smaller Number first.

样例：
对于数组[1,2,7,8,5] ，返回 [0,1,2,3,2]

#ifndef C249_H#define C249_H#include<iostream>#include<vector>using namespace std;class SegmentNode{public:    int start, end, count;    SegmentNode *left, *right;    SegmentNode(int start, int end)    {        this->start = start, this->end = end, this->count = 0;        this->left = this->right = NULL;    }};class Solution {public:    /*    * @param A: an integer array    * @return: A list of integers includes the index of the first number and the index of the last number    */    vector<int> countOfSmallerNumberII(vector<int> &A) {        // write your code here        vector<int> v;        SegmentNode *node = build(0, 10000);        for (int i = 0; i<A.size(); ++i)        {            v.push_back(query(node, 0, A[i] - 1));            modify(node, A[i]);        }        return v;    }    SegmentNode *build(int start, int end)    {        if (start > end)            return NULL;        SegmentNode *node = new SegmentNode(start, end);        if (start == end)            return node;        node->left = build(start, (start + end) / 2);        node->right = build((start + end) / 2 + 1, end);        return node;    }    void modify(SegmentNode *root, int index)    {        if (!root)            return;        if (root->start == root->end&&root->start==index)        {            root->count++;            return;        }        int mid = (root->start + root->end) / 2;        if (index<=mid)            modify(root->left, index);        else            modify(root->right, index);        root->count = root->left->count + root->right->count;    }    int query(SegmentNode *root, int start, int end)    {        if (start > end || root == NULL || start<root->start || end>root->end)            return 0;        if (start == root->start&&end == root->end)            return root->count;        if (end <= root->left->end)            return query(root->left, start, end);        else if (start >= root->right->start)            return query(root->right, start, end);        else        {            int l = query(root->left, start, root->left->end);            int r = query(root->right, root->right->start, end);            return l + r;        }    }};#endif