417. Pacific Atlantic Water Flow

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問題

Input: 
    heights = [[1,2,2,3,5],
               [3,2,3,4,4],
               [2,4,5,3,1],
               [6,7,1,4,5],
               [5,1,1,2,4]]
Output: 
    [[0,4],[1,3],[1,4],[2,2],[3,0],[3,1],[4,0]]
Explanation: 
    flow to the Pacific and Atlantic oceans, a
    [0,4]: [0,4] -> Pacific Ocean 
           [0,4] -> Atlantic Ocean
    [1,3]: [1,3] -> [0,3] -> Pacific Ocean 
           [1,3] -> [1,4] -> Atlantic Ocean
    [1,4]: [1,4] -> [1,3] -> [0,3] -> Pacific Ocean 
           [1,4] -> Atlantic Ocean
    [2,2]: [2,2] -> [1,2] -> [0,2] -> Pacific Ocean 
           [2,2] -> [2,3] -> [2,4] -> Atlantic Ocean
    [3,0]: [3,0] -> Pacific Ocean 
           [3,0] -> [4,0] -> Atlantic Ocean
    [3,1]: [3,1] -> [3,0] -> Pacific Ocean 
           [3,1] -> [4,1] -> Atlantic Ocean
    [4,0]: [4,0] -> Pacific Ocean 
           [4,0] -> Atlantic Ocean

Idea

Solution