Revert "增加深度优先算法"

This reverts commit ea9e8fce88117412ae35a386b1e581c41c9141a0.
Revert "Revert "增加深度优先算法""

This reverts commit 29bb0320da3f69c526b08eabf150e14a9fac8795.
Merge pull request #1 from bupt1987/13-06-15

13 06 15