Sorting numbers in an array without sort function
显示 更早的评论
Hello,
I want to sort numbers in an arrey without using sort function, but with bubblesort (swapping number next each other until all numbers are sorted)
Here is what I have...
X=[10 1 29 89 5 56 76 8];
finished=0;
while finished==0
if finished==0
for i=1:size(X,2)-1
if X(i)>X(i+1)
c=X(i);
X(i)=X(i+1);
X(i+1)=c;
end
end
end
if X(i)<X(i+1) || X(i)==X(i+1)
finished=1;
end
end
disp(X)
I understand that this loop works by comparing numbers next each other (like comparing 10 with 1). Then, if the front number (10) is bigger than the next number (1), the numbers are swaped. However, I want to break the loop once all numbers are sorted from the minimum number to the maximum number.
The code above only sorts the numbers until [1,10,29,5,56,76,8,89], so I want to loop several more to complete the sorting, but I want the code stops when the sorting is done. Otherwise, the code keeps on looping again and again.
I really appreciate if I get some help with this problem.
采纳的回答
James Tursa
2019-11-27
Simply set your "finished" flag depending on whether a swap was done or not. E.g.,
while true
finished = 1;
for i=1:size(X,2)-1
if X(i)>X(i+1)
c=X(i);
X(i)=X(i+1);
X(i+1)=c;
finished = 0;
end
end
if finished
break
end
end
The for-loop can also be shortened by realizing that after each pass you are guaranteed to have one more element sorted at the bottom. I.e., the for-loop doesn't have to examine the entire array each time ... at each iteration you only have to examine one fewer elements.
4 个评论
Takashi Fukushima
2019-11-27
James Tursa
2019-11-27
编辑：James Tursa
2019-11-27
If you do the entire for-loop and don't do any swaps, then the array is already sorted and you are done. In this case the "finished" flag will be 1 because it was never set to 0 inside the swapping code. So you simply test for this condition right after the for-loop is done.
the cyclist
2019-11-27
编辑：the cyclist
2019-11-27
In case you were asking something different ... the syntax
if finished
works because when the variable finished takes the value "1", that value will be converted to the boolean "true", and the if statement will be entered. In general, the condition always has to be evaluated to true/false.
I would argue that slightly better programming practice would have been to define the variable finished as a boolean false in the first place. But that's fairly precious. It's more important to get the code to work correctly first, before worrying about such nuances.
Takashi Fukushima
2019-11-28
更多回答（1 个）
the cyclist
2019-11-27
编辑：the cyclist
2019-11-27
if all(diff(X)) >= 0
Also, rather than defining the finished variable, you could have just made that the condition for the while loop:
while not(all(diff(X)) >= 0)
or, mathematically equivalently but a bit more elegantly
while any(diff(X)) < 0
类别
在 帮助中心 和 File Exchange 中查找有关 Shifting and Sorting Matrices 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
