摘要：
David has a white board with 2×N2 \times N2×N grids.He decides to paint some grids black with his brush.He always starts at the top left corner and en 阅读全文
摘要：
Give a string SSS and NNN string TiT_iTi , determine whether TiT_iTi is a subsequence of SSS. If ti is subsequence of SSS, print YES,else print NO. 阅读全文