leetcode Merge Intervals

/*****************************************************************
created:    2014/09/13 21:32
filename:    merge-intervals.cpp
author:        Justme0 (http://blog.csdn.net/justme0)

purpose:    合并交叉的区间
https://oj.leetcode.com/problems/merge-intervals/
*****************************************************************/

#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <vector>
#include <algorithm>
#include <cassert>
using namespace std;

struct Interval {
    int start;
    int end;

    Interval() : start(0), end(0) {}
    Interval(int s, int e) : start(s), end(e) {}
};

/**
 * Definition for an interval.
 * struct Interval {
 *     int start;
 *     int end;
 *     Interval() : start(0), end(0) {}
 *     Interval(int s, int e) : start(s), end(e) {}
 * };
 */
class Solution {
public:
    vector<Interval> merge(vector<Interval> &intervals) {
        if (intervals.empty()) {
            return vector<Interval>();
        }

        vector<Point> coordinates;
        for (auto iter = intervals.begin(); iter != intervals.end(); ++iter) {
            coordinates.push_back(Point(iter->start, true));
            coordinates.push_back(Point(iter->end, false));
        }
        sort(coordinates.begin(), coordinates.end(), cmp);

        int depth = 0;    // 覆盖的深度
        assert(coordinates.front().isLeft);
        vector<Interval> merged_itvs;
        int start = 0;
        for (auto iter = coordinates.begin(); iter != coordinates.end(); ++iter) {
            assert(depth >= 0);
            if (0 == depth) {
                start = iter->x;    // 此时“栈空”，iter 指向左端点，开始合并一个区间
            }
            iter->isLeft ? ++depth : --depth;
            if (0 == depth) {
                merged_itvs.push_back(Interval(start, iter->x));    // 此时“栈空”，iter 指向右端点，确定了一个区间
            }
        }

        return merged_itvs;        // 接口设计得不好
    }

    struct Point {
        int x;
        bool isLeft;

        Point() : x(0), isLeft(false) {}

        Point(int _x, bool _isLeft) : x(_x), isLeft(_isLeft) {}

//         bool operator<(const Point &other) const {
//             if (this->x < other.x) {
//                 return true;
//             } else if (this->x > other.x) {
//                 return false;
//             } else if (this->isLeft == other.isLeft) {
//                 return this < &other;
//             } else {
//                 return this->isLeft;
//             }
//         }
    };

    static bool cmp(const Point &a, const Point &b) {
        if (a.x < b.x) {
            return true;
        } else if (a.x > b.x) {
            return false;
        } else if (a.isLeft == b.isLeft) {
            return false;
        } else {
            return a.isLeft;
        }
    }

};

int main(int argc, char **argv) {
    freopen("cin.txt", "r", stdin);

    vector<Interval> vec;
    int a, b;
    while (cin >> a >> b) {
        vec.push_back(Interval(a, b));
    }

    vector<Interval> ans = Solution().merge(vec);
    for (auto ite = ans.begin(); ite != ans.end(); ++ite) {
        cout << ite->start << ' ' << ite->end << endl;
    }

    system("PAUSE");
    return 0;
}