leetcode Merge Intervals

思路:

以区间的左边为键值, 对区间进行排序
然后找出重复的部分, 如果重复就判断是否需要更新区间
如果没有重复就将当前的区间加入到 vector 中

/**
 * 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:
    static bool cmp(Interval a, Interval b) {
        return a.start < b.start;
    }
    vector<Interval> merge(vector<Interval> &intervals) {
        int size = intervals.size();
        if (size == 0 || size == 1) return intervals;
        sort(intervals.begin(), intervals.begin()+size, cmp);

        vector <Interval> new_vec;

        int start = intervals[0].start;
        int end = intervals[0].end;

        for (int i = 1; i < size; i++) {
            if (intervals[i].start <= end) {   // 如果可以合并
                if (end < intervals[i].end) {  // 判断是否要增大右边
                    end = intervals[i].end;
                }
            } else {
                new_vec.push_back(Interval(start, end));
// 比区间的左边小, 直接加入到集合中
                start = intervals[i].start;
                end = intervals[i].end;
            }
        }
        new_vec.push_back(Interval(start, end));
// 最后一个区间的时候我们已经退出循环

        return new_vec;
    }
};

// CreateTime: 2015-04-22 22:19:00

#include <isotream>
#include <cstdio>
#include <algorithm>

using namespace std;

typedef pair<int, int> Interval;

bool cmp(Interval a, Interval b) {
    return a.first < b.first;
}

int main(void) {
    vector<Interval> interval;
    // interval.push_back(make_pair(1, 4));
    // interval.push_back(make_pair(1, 4));
    interval.push_back ( make_pair (1,  3));
    interval.push_back ( make_pair (2,  6));
    interval.push_back ( make_pair (5,  7));
    interval.push_back ( make_pair (8,  10));
    interval.push_back ( make_pair (9,  12));
    interval.push_back ( make_pair (11, 18));
    int size = interval.size();
    sort(interval.begin(), interval.begin()+size, cmp);
    vector <Interval> new_vec;

    int start = interval[0].first;
    int end = interval[0].second;

    for (int i = 1; i < size; i++) {
        if (interval[i].first <= end) {
            if (end < interval[i].second) {
                end = interval[i].second;
            }
        } else {
            new_vec.push_back(Interval(start, end));
            start = interval[i].first;
            end = interval[i].second;
        }
    }
    new_vec.push_back(Interval(start, end));
    int size_2 = new_vec.size();
    for (int i = 0; i < size_2; i++) {
        printf("%d  %d\n", new_vec[i].first, new_vec[i].second);
    }

    return 0;
}