/*fn swap<'a>(a: &'a mut String, b:&'a mut String){let tmp = *a;*a = *b;*b = tmp;}let mut a = "aaa".to_string();let mut b = "bbb".to_string();swap(&mut a, &mut b);*/let mut a = 111;let mut b = 222;fn swap<'a>(a: &'a mut i32, b:&'a mut i32){let tmp = *a;*a = *b;*b = tmp;}/*fn swap(mut a:  i32, mut b:  i32){let tmp = a;a = b;b = tmp;}swap( a,  b);*/swap(&mut a, &mut b);

最高效方式

    let mut a = "aaa".to_string();let mut b = "bbb".to_string();std::mem::swap(&mut a, &mut b);