leetcode:the skyline problem

class Solution{public:    struct node    {        int x, heightIndex;        bool leftOrRight;        node(int _x, int _heightIndex, bool _leftOrRight):x(_x), heightIndex(_heightIndex), leftOrRight(_leftOrRight) {}    };    static bool cmp(const node & a, const node & b)//去掉static报错    {        if(a.x != b.x)            return a.x < b.x;//小于号不能换成减号        return a.leftOrRight < b.leftOrRight;    }    vector<pair<int, int> > getSkyline(vector<vector<int> >& buildings)    {        vector<pair<int, int> > res;        vector<node> edge;        vector<int> height;        int i, index;        for(i = 0; i < buildings.size(); i++)        {            index = height.size();            edge.push_back(node(buildings[i][0], index, false));            edge.push_back(node(buildings[i][1], index, true));            height.push_back(buildings[i][2]);        }        sort(edge.begin(), edge.end(), cmp);        multiset<int> active;        int currentHeight = 0, newHeight, newX;        for(i = 0; i < edge.size(); i++)        {            if(edge[i].leftOrRight == false)            {                active.insert(edge[i].heightIndex);                newHeight = height[edge[i].heightIndex];                newX = edge[i].x;                while(i + 1 < edge.size() && edge[i].x == edge[i + 1].x && edge[i + 1].leftOrRight == false)                {                    active.insert(edge[i + 1].heightIndex);                    newHeight = max(newHeight, height[edge[i + 1].heightIndex]);                    i++;                }                if(currentHeight < newHeight)                {                    res.push_back(make_pair(newX, newHeight));                    currentHeight = newHeight;                }            }            else            {                active.erase(edge[i].heightIndex);                newHeight = height[edge[i].heightIndex];                newX = edge[i].x;                while(i + 1 < edge.size() && edge[i].x == edge[i + 1].x && edge[i + 1].leftOrRight == true)                {                    active.erase(edge[i + 1].heightIndex);                    newHeight = max(newHeight, height[edge[i + 1].heightIndex]);                    i++;                }                if(currentHeight == newHeight)                {                    multiset<int> :: iterator it;                    int maxHeight = 0;                    for(it = active.begin(); it != active.end(); it++)                        maxHeight = max(maxHeight, height[*it]);                    if(newHeight > maxHeight)                    {                        res.push_back(make_pair(newX, maxHeight));                        currentHeight = maxHeight;                    }                }            }        }        return res;    }};