usage, so it is something I usually want to examine when joining a distressed
if(x != MAP_FAILED) return x;
，这一点在夫子中也有详细论述
���f�B�A�ꗗ | ����SNS | �L���ē� | ���₢���킹 | �v���C�o�V�[�|���V�[ | RSS | �^�c���� | �̗p���� | ������
* 核心思路：找初始无序边界 + 计算区间最值 + 扩展边界