數據結構與算法（三）數組與鏈表編程實踐

1.支持動態擴容的數組

public class DynamicArray {
        //擴容因子
        final float factor = 0.75f;
        int size = 16;
        int currentIndex = 0;
        int[] arrays = new int[size];


        private void put(int num) {
            
            if (currentIndex > size * factor) {
                //擴容並轉移數據
                int newSize = size * 2;
                size = newSize;
                int[] newArray = new int[newSize];
                for (int i = 0; i < currentIndex; i++) {
                    newArray[i] = arrays[i];
                }
//            也可以用下面的方法來做數組拷貝
//            if (currentIndex >= 0)
//                System.arraycopy(arrays, 0, newArray, 0, currentIndex);
                arrays = newArray;
            }
            arrays[currentIndex] = num;
            currentIndex++;

//            for (int i = 0; i < currentIndex; i++) {
//                System.out.print("num=" + num + "  current=" + arrays[i] + "\n");
//            }
//            System.out.println("   ");
        }

        private int get(int index){
            return arrays[index];
        }
    }

測試代碼：

  @Test
    public void Test() {
        DynamicArray dynamicArray = new DynamicArray();
        for (int i = 0; i < 100; i++) {
            dynamicArray.put(i);
        }

        System.out.println(" 下標88的值是 "+dynamicArray.get(88));
    }

2.兩個有序數組合併爲一個

private void arrayMerge() {
        int[] a1 = new int[]{3, 3, 5, 7, 9};
        int[] a2 = new int[]{2, 4, 6, 8, 10,13,16};

        int[] mergeA = new int[a1.length+a2.length];
        int i1 = 0, i2 = 0;
        for (int i = 0; i < mergeA.length; i++) {
            int temp;
            if (a1[i1] < a2[i2]) {
                //插入a1數組的值
                temp = a1[i1];
                if (i1 < a1.length - 1)
                    i1++;
                else {
                    a1[i1] = Integer.MAX_VALUE;
                }
            } else {
                temp = a2[i2];
                if (i2 < a2.length - 1)
                    i2++;
                else {
                    a2[i2] = Integer.MAX_VALUE;
                }
            }
            mergeA[i] = temp;
            System.out.println("數組第" + i + "個值是" + temp);
        }
    }

時間複雜度O(n)

3.支持增刪的有序數組

    class SortedArray {
        int[] arrays = new int[10];
        int index = 0;
        int temp = -1;//標記要插入的值是否是最大值

        private void insert(int des) {
            if (index >= arrays.length) {
                System.out.println("滿啦");
                return;
            }
            for (int i = 0; i < index; i++) {
                if (des < arrays[i]) {
                    temp = arrays[index - 1];
                    for (int j = index; j > i; j--) {
                        arrays[j] = arrays[j - 1];
                    }
                    arrays[i] = des;
                    //移動完畢，跳出循環
                    break;
                }
            }
            if (temp < 0) {
                //如果是數組目前的最大值，直接插入
                arrays[index] = des;
            } 


            index++;
            temp = -1;
        }

        private void delete(int sub) {
            for (int i = sub; i < arrays.length - 1; i++) {
                arrays[i] = arrays[i + 1];
            }
            arrays[arrays.length - 1] = 0;
        }

        private void arrayInfo() {
            for (int i = 0; i < arrays.length; i++) {
                System.out.println("第" + i + "個元素是" + arrays[i]);
            }
        }
    }