leetcode_c++:Divide and Conquer：The Skyline Problem（218）

题目

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class Solution {public:    vector<pair<int, int>> getSkyline(vector<vector<int>>& buildings) {        vector< pair<int, int> > edges;        //put all of edge into a vector        //set left edge as negtive, right edge as positive        //so, when we sort the edges,         //  1) for same left point, the height would be descending order        //  2) for same right point, the height would be ascending order        int left, right, height;        for(int i=0; i<buildings.size(); i++) {            left   = buildings[i][0];            right  = buildings[i][1];            height = buildings[i][2];            edges.push_back(make_pair(left, -height));            edges.push_back(make_pair(right, height));        }        sort(edges.begin(), edges.end());        // 1) if we meet a left edge, then we add its height into a `set`.        //    the `set` whould sort the height automatically.        // 2) if we meet a right edge, then we remove its height from the `set`        //        // So, we could get the current highest height from the `set`, if the         // current height is different with preivous height, then we need add        // it into the result.        vector< pair<int, int> > result;        multiset<int> m;        m.insert(0);        int pre = 0, cur = 0;        for (int i=0; i<edges.size(); i++){            pair<int,int> &e = edges[i];            if (e.second < 0) {                m.insert(-e.second);            }else{                m.erase(m.find(e.second));            }            cur = *m.rbegin();            if (cur != pre) {                result.push_back(make_pair(e.first, cur));                pre = cur;            }        }        return result;    }};