# 1. 选择排序

一句话总结：

> n^2遍历，每遍历一轮选择一个最小/大值，
>
> 然后与当前位替换，最终得到排序结果

python

```python
class Sort:
    def sort(self):
        pass

    def less(self, a, b):
        return a < b

    def swap(self, nums, i, j):
        nums[i], nums[j] = nums[j], nums[i]


class Selection(Sort):
    def sort(self, nums):
        n = len(nums)
        for i in range(n):
            min = i
            for j in range(i + 1, n):# 第二轮每次选择出后面元素中最小的，并记录最小位置
                if self.less(nums[j], nums[min]):
                    min = j
            self.swap(nums, i, min) #结束选择后，直接最小位置和i号互换


if __name__ == '__main__':
    arr = [5, 1, 8, 7, 10, 6, 9, 5, 20, 3, 0]
    print(arr)
    sort = Selection()
    sort.sort(arr)
    print(arr)
```

java

```java
package sort;

public abstract class Sort<T extends Comparable<T>> {
    public abstract void sort(T[] nums);

    public boolean less(T v,T w){
        return v.compareTo(w)<0;
    }

    public void swap(T[] a,int i,int j){
        T t=a[i];
        a[i]=a[j];
        a[j]=t;
    }
}


public class Selection<T extends Comparable<T>> extends Sort<T>{
    @Override
    public void sort(T[] nums) {
        int n=nums.length;
        for(int i=0;i<n;i++){
            int min=i;
            for(int j=i+1;j<n;j++){
                if(less(nums[j],nums[min])) min=j;
            }
            swap(nums,i,min);
        }
    }

    public static void main(String[] args){
        Integer[] arr={
                5,1,8,7,10,6,9,5,20,3,0
        };
        Sort<Integer> sort=new Selection<>();
        sort.sort(arr);
        ArrayUtils.printArray(arr);
    }
}
```


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