# Selection Sort

## 思路

不断地选择剩余元素中的最小者。

* 找到数组中最小元素并将其和数组第一个元素交换位置。
* 在剩下的元素中找到最小元素并将其与数组第二个元素交换，直至整个数组排序。

![](/files/-Lpv9zpYxma2VOPBKQNK)

## 复杂度分析

**Best**： $$\Omega(n^2)$$\
**Worst**: $$O(n^2)$$\
**Average**: $$\Theta(n^2)$$

```java
package selectionSort;

public class SelectionSort {
    public static void main(String[] args) {
        int[] unsortedArray = new int[] { 8, 5, 2, 6, 9, 3, 1, 4, 0, 7 };
        selectionSort(unsortedArray);
        System.out.println("After Sort: ");
        printArr(unsortedArray);
    }

    private static void selectionSort(int[] arr) {
        int len = arr.length;
        for (int i = 0; i < len; i++) {
            printArr(arr);
            System.out.println();
            int minIndex = i;
            for (int j = i; j < len; j++) {
                if (arr[j] < arr[minIndex]) {
                    minIndex = j;
                }
            }
            swap(arr, minIndex, i);
        }
    }

    private static void swap(int[] arr, int i, int j) {
        int tmp = arr[i];
        arr[i] = arr[j];
        arr[j] = tmp;
    }

    private static void printArr(int[] arr) {
        for (Integer num : arr) {
            System.out.print(num + " ");
        }
    }
}
```


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