題意：比如有一陣列[2, 4, 3, 1, 5]，求5拆分成兩個數，這兩個數在陣列下標集合為0,2和1,3

程式碼

public static Map<Integer, Integer> getIndex(List<Integer> list, int a) {
    // 數拆分成兩個數在陣列中兩個下標的map
    Map<Integer, Integer> indexMap = new HashMap<>();
    if (null == list || list.size() <= 0 || a < 2) {
        
 
return indexMap;
    }

    // 陣列中的數與下標的map
    Map<Integer, Integer> numberIndexMap = new HashMap<>();
    for (int index = 0, size = list.size(); index < size; index++) {
        numberIndexMap.put(list.get(index), index);
    }
    Integer integerX;
    Integer integerY;
    for (int i = 1, x = 1, y = a - 1; x < y; i++, x = i, y = a - i) {
        integerX 
 
= numberIndexMap.get(x);
        integerY = numberIndexMap.get(y);
        if (null != integerX && null != integerY) {
            indexMap.put(integerX, integerY);
        }
    }
    return indexMap;
}