算法-選擇排序

選擇排序就是每一輪選出最小者交換到左側的思路,或者選出最大這交換到最右側的思路
這種排序的最大優勢就是省去多餘的元素交換
OC代碼:

- (NSArray *)selectSort:(NSArray *)sort
{
    NSMutableArray *array = [NSMutableArray arrayWithArray:sort];
    for (int i =0; i < array.count -1; i++) {
        int minIndex = i;
        for (int j = i+1; j < array.count; j++) {
            if([array[minIndex] intValue] > [array[j] intValue]){
                minIndex = j;
            }
        }
        if (minIndex !=  i ) {
            [array exchangeObjectAtIndex:i withObjectAtIndex:minIndex];
        }
    }
 
    return [NSArray arrayWithArray:array];
}
- (void)viewDidLoad {
    [super viewDidLoad];
    NSArray *array = @[@3,@4,@5,@7,@9,@10,@2,@(-11),@8,@13,@1];
    NSArray *list = [self selectSort:array];
    NSLog(@"list = %@",list);
}
打印結果:list = (
    "-11",
    1,
    2,
    3,
    4,
    5,
    7,
    8,
    9,
    10,
    13
)

java代碼:
 

	public static void selectionSort(int[] array){
		for(int i =0; i<array.length -1; i++){
			int minIndex = 1;
			for (int j = i +1; j < array.length; j++) {
				minIndex = array[minIndex] < array[j] ? minIndex : j;
			}
			int temp = array[i];
			array[i] = array[minIndex];
			array[minIndex] = temp;
		}
	}
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub

		int[] array = new int[]{3,4,2,1,5,6,7,30,50,-4,7,0};
		selectionSort(array);
		System.out.println(Arrays.toString(array));
	}

時間複雜度爲O(n^2)  空間複雜度O(1)

參考:https://mp.weixin.qq.com/s/dGfh2t7xhg0wMM_DcYP1Cw