Matlab Cody (1)
Size refers to the number of nodes in a parse tree. Generally speaking, you can think of size as code length.
What is Cody? see here
Problem 1. Times 2 - START HERE
function y = times2(x)
y = bitshift(x,1); % size=13
end
function y = times2(x)
y = 2*x; % size=12 (same as y=x+x)
end
function ans = times2(x)
2*x; % size=10 (best)
end
Problem 2. Make the vector [1 2 3 4 5 6 7 8 9 10]
function x = oneToTen
x = [1 2 3 4 5 6 7 8 9 10]; % size=20
end
function x = oneToTen
x = 1:10; % size=11
end
function ans = oneToTen
1:10; % size=9 (best)
end
function ans = oneToTen
colon(1,10); % size=10
end
function ans = oneToTen
linspace(1,10,10); % size=11
end
function x = oneToTen
x = cumsum(ones(1,10)); % size=14
end
Problem 3. Find the sum of all the numbers of the input vector
function ans = vecsum(x)
sum(x); % size=10 (best)
end
function y = vecsum(x)
y = sum(x(:)); % size=14 (useful for matrix)
end
function y = vecsum(x)
n = length(x);
y = 0;
for i = 1:n
y = y + x(i); % size=30
end
end
Problem 4. Make a checkerboard matrix
function a = checkerboard(n)
a(1:2:n,1:2:n) = 1;
a(2:2:n,2:2:n) = 1; % size=36
end
function ans = checkerboard(n)
invhilb(n)>0; % size=12 (best)
end
function a = checkerboard(n)
a1 = repmat([1,0;0,1],n,n);
a = a1(1:n,1:n); % size=31
end
function a = checkerboard(n)
for i=1:n
for j=1:n
a(i,j)=mod(i+j+1,2); % size=32
end;
end;
end
Problem 5. Triangle Numbers
function ans = triangle(n)
sum(1:n); % size=12 (best)
end
function ans = triangle(n)
n*(n+1)/2; % size=15
end
Problem 6. Select every other element of a vector
function ans = everyOther(x)
x(1:2:end); % size=15 (best)
end
function ans = everyOther(x)
x(1:2:length(x)); % size=16 (same as x(1:2:numel(x)))
end
function x = everyOther(x)
x(2:2:end) = []; % size=18
end
ps: 对于m-by-n的矩阵x，numel(x)=m*n, length(x)=n.
Problem 7. Column Removal
function B = column_removal(A,n)
A(:,n) = [];
B = A; % size=19
end
function A = column_removal(A,n)
A(:,n) = []; % size=15
end
function A = column_removal(A,n)
A(:,n) = ''; % size=14 (best)
end
function ans = column_removal(A,n)
A(:,[1:n-1,n+1:end]); % size=24
end
function ans = column_removal(A,n)
A(:,1:end ~= n); % size=17
end
Problem 8. Add two numbers
function ans = add_two_numbers(a,b)
a+b; % size=11
end
Problem 9. Who Has the Most Change?
function a = most_change(a)
[~,a]=max(a*[.25;.05;.1;.01]); % size=24
end
function b = most_change(a)
[~,b]=max(sum(bsxfun(@times,a,str2num('[0.25,0.05,0.10,0.01]')),2)); % size=24
end
function b = most_change(a)
total = a * [25 5 10 1]';
b = find(total==max(total)); % size=28
end
function b = most_change(a)
[~,b] = max(a * str2num('[0.25; 0.05; 0.1; 0.01]')); % size=18 (best)
end
Problem 10. Determine whether a vector is monotonically increasing
function ans = mono_increase(x)
isequal(unique(x), x); % size=13 (best)
end
function ans = mono_increase(x)
mean(diff(x)>0)==1 | isempty(diff(x))==1; % size=24
end
function ans = mono_increase(x)
all(diff(x)>0); % size=14
end
Problem 26. Determine if input is odd
function ans = is_it_odd(n)
bitand(n,1); % size=11 (best)
end
function ans = is_it_odd(n)
mod(n,2); % size=11 (best)
end
function ans = is_it_odd(n)
rem(n,2); % size=11 (best)
end
function ans = is_it_odd(n)
1-(round(n/2)==n/2); % size=19
end