找到给定数组中的子数组，其中元素按升序排列，并且最后一个元素与该子数组的第一个元素之间的最大差值

正常的实现方法

public class Test{

	private static int[] arr;
	
	public static int subArray(){
		if(null == arr){
			return 0;
		}
    	int index = 1;
    	int c = 0;
    	int[] num1 = null;
		List<Integer> list = new ArrayList<Integer>();
		for(int i = index; i < arr.length; i++){
			if(arr[i-1] <= arr[i]){
				index++;
			}else{
				num1 = Arrays.copyOfRange(arr, c, index);
				int max = maxInterval(num1);
				list.add(max);
				System.out.println(Arrays.toString(num1));
				c = index;
				index++;
			}
		}
		if(index == arr.length){
			num1 = Arrays.copyOfRange(arr, c, index);
			int max = maxInterval(num1);
			list.add(max);
			System.out.println(Arrays.toString(num1));
		}
		Object[] obj = list.toArray();
		Arrays.sort(obj);
		return (int) obj[obj.length-1];
	}
	
	public static int maxInterval(int[] arr){
		int maxValue = 0;
		if(null != arr){
			maxValue = arr[arr.length - 1] - arr[0];
		}
		return maxValue;
	}
	
	public static void main(String[] args){
		// int[] arrays = new int[]{1, 1, 2, 4, 6, 0, 3, 1, 9, 2, 2, 3};
		int maxSum = subArray(arrays);
		System.out.println("最大子数组的差异为：" + maxSum);
	}
}

递归的实现方法

public class Test{

	private static int[] arr;
	
	public static int maxInterval(){
		if(arr.length == 1){
			return arr[0];
		}
		if(arr.length == 2){
			if(arr[0] > arr[1]){
				return -1;
			}else{
				return arr[1]-arr[0];
			}
		}
		return findMaxValue(arr, 0);
	}
	
	public static int findMaxValue(int[] arr, int maxValue) {
        int startIndex = 0;
        for (int i = 1; i < arr.length; i++) {
            if (arr[i] < arr[i - 1]) {
                int[] ints = Arrays.copyOfRange(arr, i, arr.length);
                int maxVal = arr[i - 1] - arr[0];
                maxValue = maxVal < maxValue ? maxValue : maxVal;
                return findMaxValue(ints, maxValue);
            }
            if (i == arr.length - 1) {
                int[] ints = Arrays.copyOfRange(arr, startIndex, arr.length);
                int maxVal = ints[ints.length - 1] - ints[0];
                maxValue = maxVal < maxValue ? maxValue : maxVal;
            }
        }
        return maxValue;
    }
	
	public static void main(String[] args){
		System.out.println("最大子数组的差异为：" + maxInterval());
	}	
}