## 精彩预告

[0042.trapping-rain-water](./problems/42.trapping-rain-water.md):

<img width="300" src="https://tva1.sinaimg.cn/large/007S8ZIlly1ghlueqdwy3j30bg04hmx3.jpg">

[0547.friend-circles](./problems/547.friend-circles-en.md):

<img width="600" src="./assets/problems/547.friend-circle-bfs.png">

[backtrack problems](./problems/90.subsets-ii.md):

<img width="600" src="./assets/problems/backtrack.png">

[0198.house-robber](./problems/198.house-robber.md):

<img width="600" src="./assets/problems/198.house-robber.png">

[0454.4-sum-ii](./problems/454.4-sum-ii.md):

<img width="600" src="./assets/problems/454.4-sum-ii.png">
