private static void selectSort(int[] arr) {
		int i;//i代表已经排好序的个数 
		for(i=0; i<=arr.length-1; i++){
			//找到arr[i]到最后的所有数中的最小值，其索引为smallest
			int smallestIndex = i;
			for(int j =i; j<=arr.length-1; j++){
				if(arr[j] < arr[smallestIndex]){
					smallestIndex = j;
				}
			}
			//交换arr[smallestIndex]和arr[i]
			int temp = arr[smallestIndex];
			arr[smallestIndex] = arr[i];
			arr[i] = temp;
		}
	}