/***************************************************************************************************
Given a collection of intervals, merge all overlapping intervals.
For example,
Given [1,3],[2,6],[8,10],[15,18],
return [1,6],[8,10],[15,18].
***************************************************************************************************/
#include<stdio.h>struct Interval {int start;int end;
};/*按区间起点排序*/
int cmp(const void *a , const void *b){struct Interval *intval1 = (struct Interval *)a;struct Interval *intval2 = (struct Interval *)b;return intval1->start - intval2->start;
}/*** Definition for an interval.* struct Interval {*     int start;*     int end;* };*/
/*** Return an array of size *returnSize.* Note: The returned array must be malloced, assume caller calls free().*/
struct Interval* merge(struct Interval* intervals, int intervalsSize, int* returnSize) {if(intervalsSize == 0){//数组为0*returnSize = 0;return NULL;}if(intervalsSize == 1){//只有一个区间*returnSize = 1;struct Interval *retIntv = (struct Interval*)malloc(sizeof(struct Interval));retIntv[0].start = intervals[0].start;retIntv[0].end = intervals[0].end;return retIntv;}qsort(intervals,intervalsSize,sizeof(struct Interval),cmp);//排序int length = 0,end = 0;int *starts = (int *)malloc(intervalsSize*sizeof(int));int *ends = (int *)malloc(intervalsSize*sizeof(int));memset(starts,-1,intervalsSize*sizeof(int));memset(ends,-1,intervalsSize*sizeof(int));for(int i = 0;i < intervalsSize;i++){starts[length] = intervals[i].start;ends[length] = intervals[i].end;while(i < intervalsSize - 1 && ends[length] >= intervals[i + 1].start){//合并前一个终点大于后一个的起点的区间i++;ends[length] = ends[length] > intervals[i].end ? ends[length] : intervals[i].end;}length++;}struct Interval *retIntv = (struct Interval*)malloc(length*sizeof(struct Interval));for(int i = 0;i < length;i++){retIntv[i].start = starts[i];retIntv[i].end = ends[i];}free(starts);free(ends);*returnSize = length;return retIntv;
}void main(){//[1,3],[2,6],[8,10],[15,18]//[1,6],[2,3],[8,10],[15,18]//[1,6],[8,10],[2,3],[15,18]struct Interval *intervals = (struct Interval *)malloc(1*sizeof(struct Interval));intervals[0].start = 1;intervals[0].end = 6;//intervals[1].start = 5;//intervals[1].end = 10;//intervals[2].start = 2;//intervals[2].end = 3;//intervals[3].start = 15;//intervals[3].end = 18;int length = 0;struct Interval *retIntv = merge(intervals,1,&length);for(int i = 0;i < length;i++){printf("[%d,%d]\n",retIntv[i].start,retIntv[i].end);}free(intervals);free(retIntv);
}