在一维坐标轴上有n个区间段，求重合区间最长的两个区间段。

//重叠区间数
#define N 2

typedef struct arrange {
	int x;
	int y;
} Arrange;

//先按左边界排序,若相等再按右边界排序(升序)
int cmp(const void* a1, const void* a2) {
	if ((*(const Arrange*) a1).x == (*(const Arrange*) a2).x) {
		return (*(const Arrange*) a1).y - (*(const Arrange*) a2).y;
	} else {
		return (*(const Arrange*) a1).x - (*(const Arrange*) a2).x;
	}
}

void printArranges(Arrange* arranges, int len) {
	for (int i = 0; i < len; ++i) {
		cout << "x: " << arranges[i].x << " y: " << arranges[i].y << endl;
	}
}

//最大重叠区间大小
int findMaxOverlap(Arrange* arr, int len, Arrange* result, int resultSize) {
	qsort(arr, len, sizeof(Arrange), cmp);

	Arrange pivot = arr[0];
	int maxOverlap = 0;

	for (int i = 1; i < len; ++i) {
		//区间不重叠
		if (pivot.y < arr[i].x) {
			pivot = arr[i];
			continue;
		} else {
			//arr[i]包含在pivot内
			if (pivot.y >= arr[i].y) {
				if (maxOverlap < arr[i].y - arr[i].x) {
					maxOverlap = arr[i].y - arr[i].x;
					result[0] = pivot;
					result[1] = arr[i];
				}
			} else {
				if (maxOverlap <= pivot.y - arr[i].x) {
					maxOverlap = pivot.y - arr[i].x;
					result[0] = pivot;
					result[1] = arr[i];
				}
				pivot = arr[i];
			}
		}
	}
	return maxOverlap + 1;
}