Searching Earthquake Data(2)

2017-11-2(四)

Programming Exercise: Searching Earthquake Data(2)

今天完成剩下4個assignment

1. Filtering by Depth

2. Filtering by Phrase in Title

3. Finding the Closest Earthquakes to a Location

4. Finding the Largest Magnitude Earthquakes

Assignment 2: Filtering by Depth

• code link

• 基本的depth大小判定

• Output 圖片

Assignment 3: Filtering by Phrase in Title

• code link

• 關鍵在判斷出phase在info的哪一個位置，是start, end, any三種情況，

• title.startsWith(phrase) 這是重要語法

• 如圖：

Assignment 4: Finding the Closest Earthquakes to a Location

• code link
• 因為不是找出最短距離，而是找出最小的4個最短距離，所以要有index去判斷每一個排序的data

• 如圖：
• 關鍵code如下：

public ArrayList<QuakeEntry> getClosest(ArrayList<QuakeEntry> quakeData, Location current, int howMany) {
        ArrayList<QuakeEntry> ret = new ArrayList<QuakeEntry>();
        // TO DO
        for(int i=0; i< howMany; i++){
            ret.add(quakeData.get(i));
        }

        // for each quake in quakeData
        for(QuakeEntry qe:quakeData){
            // Calculate distance between quakeData quake and current location
            Location qeLocation = qe.getLocation();
            float qeDistance = current.distanceTo(qeLocation);
            System.out.println("Distance between quakeData quake and current location: " + qeDistance);

            // for each quake in ret
            for(QuakeEntry quake: ret){
                // Calculate distance between ret quake and current location

                Location qeRet = quake.getLocation();
                float retDistance = current.distanceTo(qeRet);
                System.out.println("Distance between ret quake and current location: " + retDistance);

                // If quakeData quake is closer than ret quake
                if(qeDistance < retDistance){
                    // replace ret quake with quakeData quake
                    int index = ret.indexOf(quake);
                    ret.remove(index);
                    ret.add(index, qe);

                    System.out.println(retDistance + " " + qeDistance);
                    System.out.println("Added quake to pos " + index);
                    // Check next quakeData quake
                    break;
                }
            }


        }

        System.out.println(ret.size());
        return ret;
    }

Assignment 5: Finding the Largest Magnitude Earthquakes

• code link
• 關鍵在於判斷，ArrayList largest是否已經達到 howMany的上限，還有dataRemovable裡面是否還有data，並且在執行每一次步驟時，dataRemovable裡的data要移除

 public ArrayList<QuakeEntry> getLargest(ArrayList<QuakeEntry> data, int howMany){
        ArrayList<QuakeEntry> dataRemovable = data; 
        ArrayList<QuakeEntry> largest = new ArrayList<QuakeEntry>();

        // Until either largest contains howMany elements or data runs out
        while(largest.size() < howMany || dataRemovable.size() == 0){
            int index = indexOfLargest(dataRemovable);
            largest.add(dataRemovable.get(index));
            dataRemovable.remove(index);
        }

        return largest;
    }

• 結果圖：

  

總結：

• 我覺得簡單的filter不見得就代表容易，很多skill還要逐步積累，儘管上述assignment並不是太難，但我已經花了早上將近3-4小時去implement，我明白現在還很菜，不過我知道我會越來越好的，重點是要好好做好每一個步驟。

• 當中有很多問題，像是pharse的判斷，我就不知道有startsWith() 這個語法，還有第五題我也不知道要用while，這些後來是參考別人的思路，然後才寫出來的。

• 儘管是參考他人，也要問自己，下次要用這個方法，會用在哪些場景中？能找到哪些data?

• 根據過往經驗，與其快速下一個我學到很多的經驗，不如留一些問題給自己，以便日後再回來看此筆記時，看看自己有沒有進步。

• 這種找前三名、倒數5名的邏輯，是否能用while以外的用法呢？