How to create binary search code

88 次查看（过去 30 天）
Camden Nelson
Camden Nelson 2023-2-12
回答： Raghvi 2023-2-15
I thought I had this code working yesterday but must've changed something on accident. I am not sure how to finish it to perform binary serach. It only says my value isn't present except when in the first index. See code below:
function [out] = BinSearch(x,A)
i = 1; % i is the leftmost index which is 1
j = length(A); % j is the rightmost index which is length(A)
while i < j
m = 1;
m = floor((i + j)/2); % Find middle of array
if x > A(m) % If userval is in the left half of array
i = m + 1;
else % Userval is in the right half of array
j = m;
end
end
if x == A(i) % If userval is in the first index
out = i;
else
out = ('Your number was not found in the array');
end
end
  1 个评论
Voss
Voss 2023-2-12
The function seems like it will work ok when A is non-empty and sorted. Is the A you pass to the function sorted? If you want the function to work for arbitrary A, you can sort A inside the function and also handle the case when A is empty.

请先登录，再进行评论。

请先登录，再回答此问题。

回答（1 个）

Raghvi
Raghvi 2023-2-15
Hi Camden,
I understand you are having trouble with binary search function. I believe the problem was that you were checking x with first index (i) instead of middle index m. The following code worked for me:
function [out] = BinSearch(x,A)
i = 1; % i is the leftmost index which is 1
j = length(A); % j is the rightmost index which is length(A)
flag = 0;
while i <= j
m = ceil((i + j)/2); % Find middle of array
if A(m)==x
out = m;
flag = 1;
break;
elseif x > A(m) % If userval is in the left half of array
i = m + 1;
else % Userval is in the right half of array
j = m;
end
end
if flag == 0
out = ('Your number was not found in the array');
end
end

类别

在 Help Center 和 File Exchange 中查找有关 Shifting and Sorting Matrices 的更多信息

标签

产品


版本

R2022b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by