LintCode-[中等] 612. K个最近的点

描述：
给定一些 points 和一个 origin，从 points 中找到 k 个离 origin 最近的点。按照距离由小到大返回。如果两个点有相同距离，则按照x值来排序；若x值也相同，就再按照y值排序。

样例：
给出 points = [[4,6],[4,7],[4,4],[2,5],[1,1]], origin = [0, 0], k = 3
返回 [[1,1],[2,5],[4,4]]

思路：
运用pair同时记录points里的每个点的在points里的序号和到origin点的距离存入到一个vector中。结合pair定义一个符合题意的比较大小的函数，再运用快速排序将这个vector进行排序，获得排序结果，最后根据k的值决定输出结果的前k个点。

debug总结：
快速排序运用不熟，map和pair的各自用法有点混淆。

C++实现：

/** * Definition for a point. * struct Point { * int x; * int y; * Point() : x(0), y(0) {} * Point(int a, int b) : x(a), y(b) {} * }; */
class Solution
{
public:
    /** * @param points a list of points * @param origin a point * @param k an integer * @return the k closest points */
    bool com(pair<int, float>& a, pair<int, float>& b, vector& points) {
        if (a.second > b.second) {
            return 1;
        }
        else if (a.second < b.second) {
            return 0;
        }
        else {
            if (points[a.first].x > points[b.first].x) {
                return 1;
            }
            else if (points[a.first].x < points[b.first].x) {
                return 0;
            }
            else {
                if (points[a.first].y > points[b.first].y) {
                    return 1;
                }
                else if (points[a.first].y < points[b.first].y) {
                    return 0;
                }
                else {
                    return 1;
                }
            }
        }
    }
        int quickSort(vector& points, vectorint, float>>& mapVector, int left, int right) {
            if (left < right) {
                int low = left;
                int high = right;
                pair<int, float>pivot = mapVector[left];
                while (low < high) {
                    while (low < high && com(mapVector[high], pivot, points)) {
                        high--;
                    }
                    if (low < high) {
                        mapVector[low] = mapVector[high];
                    }
                    while (low < high && com(pivot, mapVector[low], points)) {
                        low++;
                    }
                    if (low < high) {
                        mapVector[high] = mapVector[low];
                    }
                }
                mapVector[low] = pivot;
                return low;
            }
        }
        void quickSort2(vector& points, vectorint, float>>& mapVector, int left, int right) {
            int size = mapVector.size();
            if (size == 0) return;
            if (left < right) {
                int mid = quickSort(points, mapVector, left, right);
                quickSort2(points, mapVector, left, mid - 1);
                quickSort2(points, mapVector, mid + 1, right);
            }
        }
        vector kClosest(vector& points, Point& origin, int k) {
            // Write your code here
            int size = points.size();
            float distance;
            vectorint, float>>mapVector;
            for (int i = 0; i < size; i++) {
                distance = sqrt((points[i].x - origin.x) * (points[i].x - origin.x) + (points[i].y - origin.y) * (points[i].y - origin.y));
                mapVector.push_back(make_pair(i, distance));
            }
            quickSort2(points, mapVector, 0, size - 1);
            vectorresult;
            for (int i = 0; i < k; i++) {
                result.push_back(points[mapVector[i].first]);
            }
            return result;
        }
};