上官网看了原题 33 个测试点的时限分别是：0.10s,0.10s,0.10s,0.10s,0.10s,0.10s,0.10s,0.10s,0.10s,0.10s,0.10s,0.10s,0.10s,0.20s,0.40s,0.30s,1.00s,0.40s,0.40s,1.00s,1.00s,1.00s,1.50s,1.50s,2.50s,3.50s,3.00s,3.50s,7.00s,4.50s,3.00s,6.50s,5.50s，其中时限最大的测试点 7s，而此题时限 1.5s，差距较大，导致我复杂度与最优解一样但被卡常过不去。

另，空间 128M 没有问题，请求管理员改回 128M。