编辑代码

class Main {
	public static void main(String[] args) {
        //JSRUN引擎2.0，支持多达30种语言在线运行，全仿真在线交互输入输出。
		System.out.println("Hello world!   - java.jsrun.net ");
        System.out.println(arraySum1(new int[]{1,2,3},3));
        System.out.println(arraySum1(new int[]{6,2,3},3));
        System.out.println(arraySum1(new int[]{6,2,3,3,1},5));
        System.out.println(arraySum1(new int[]{6,2,3,5,1},5));
        System.out.println("======================");
        System.out.println(arraySum2(new int[]{1,2,3},3));
        System.out.println(arraySum2(new int[]{6,2,3},3));
        System.out.println(arraySum2(new int[]{6,2,3,3,1},5));
        System.out.println(arraySum2(new int[]{6,2,3,5,1},5));
	}

    //递归
    public static int arraySum1(int[] arr,int len){
        int sum=0;
        if(len>0){
            sum+=arr[0];
            for(int i=1;i<len;i++){
                arr[i-1]=arr[i];
            }
            sum+=arraySum1(arr,len-1);
        }
        return sum;
    }
    //递推
    public static int arraySum2(int[] arr,int len){
        int sum=0;
        for(int i=0;i<len;i++){
            sum += arr[i];
        }
        return sum;
    }
}