我在 MATLAB 中编写了一个堆排序函数,它工作正常,只是当输入的长度大于或等于 1000 时,它可能需要很长时间(例如 1000 的长度需要半秒)。我不确定是 MATLAB 在堆排序算法上运行得不是很快,还是只是我的代码需要改进。我的代码如下所示:
function b = heapsort(a)
[~,n] = size(a);
b = zeros(1,n);
for i = 1:n
a = build_max_heap(a);
b(n+1-i) = a(1);
temp = a(1);
a(1) = a(n+1-i);
a(n+1-i) = temp;
a(n+1-i) = [];
a = heapify(a,1);
end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function a = build_max_heap(a)
[~,n] = size(a);
m = floor(n/2);
for i = m:-1:1
a = heapify(a,i);
end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function a = heapify(a,i)
[~,n] = size(a);
left = 2*i;
right = 2*i + 1;
if left <= n
if a(left) >= a(i)
large = left;
else
large = i;
end
else
return
end
if right <= n
if a(right) >= a(large)
large = right;
end
end
if large ~= i
temp = a(large);
a(large) = a(i);
a(i) = temp;
a = heapify(a,large);
end
end
我知道可能是代码a(n+1-i) = [];
可能会消耗大量时间。但是当我将 in 更改[]
为-999
(低于输入向量的任何数量)时,它无济于事,反而花费了更多时间。