Maximum Subarray Problem -- Classic Algorithms in Matlab

조회 수: 2 (최근 30일)
Matlab2010
Matlab2010 2014년 3월 13일
댓글: Salaheddin Hosseinzadeh 2014년 3월 13일
Trying to implement some forms of this classic algorithm
Not quite there; anyone fancy having a look at the O(n log n) and O(n) attempts -- working from the PDF above.
function MaxSubArrayProblem()
clc;
A = randn(100,1);
tic;
B1=MaxSubArray_BruteForce(A); %O(n^3)
t1=toc;
tic;
B2=MaxSubArray_reUseData(A); %O(n^2)
t2=toc;
tic;
B3=MaxSubArray_divideAndConquer(A); %O(n log n)
t3=toc;
tic;
B4=MaxSubArray_revisualizing(A); %O(n)
t4=toc;
isequaln(B1,B2,B3,B4)
bar([t1 t2 t3 t4]);
end
function B= MaxSubArray_BruteForce(A)
B= NaN(length(A),3);
VMAX = -inf;
for i = 1 : length(A)
for j = i: length(A)
V = sum(A(i:j));
if(V>VMAX)
VMAX = V;
from = i;
to = j;
end
end
disp(['Largest Sum: ' num2str(VMAX) ' from ' num2str(from) ' to ' num2str(to)]);
B(i,:) = [VMAX from to];
end
end
function B= MaxSubArray_reUseData(A)
B= NaN(length(A),3);
VMAX = -inf;
for i = 1 : length(A)
V = 0;
for j = i: length(A)
V = V + A(j);
if(V>VMAX)
VMAX = V;
from = i;
to = j;
end
end
disp(['Largest Sum: ' num2str(VMAX) ' from ' num2str(from) ' to ' num2str(to)]);
B(i,:) = [VMAX from to];
end
end
function B= MaxSubArray_divideAndConquer(A)
B= NaN(length(A),3);
for i = 1: length(A)
for j = 1: length(A)
myMax = MCS(A,i,j);
end
B(i,:) = [myMax i j];
end
end
function myMax = MCS(A,i,j)
if(i==j)
myMax = A(i:j);
else
myMax1 = MCS(A,i,floor(0.5*(i+j)));
myMax2 = MCS(A,floor(0.5*(i+j))+1,j);
myMax3 = MCS(A,i,j);
myMax = max([myMax1 myMax2 myMax3]);
end
end
function B= MaxSubArray_revisualizing(A)
B= NaN(length(A),3);
VMAX = -inf;
from = 1;
T = A(1);
V = A(1);
Tmin = min(0,T);
for j = 2: length(A)
T = T + A(j);
if((T-Tmin)>V)
V = T - Tmin;
%
VMAX = V;
to = j;
end
if(T<Tmin)
Tmin = T;
from = j;
end
disp(['Largest Sum: ' num2str(VMAX) ' from ' num2str(from) ' to ' num2str(to)]);
B(j,:) = [VMAX from to];
end
end
  댓글 수: 1
Salaheddin Hosseinzadeh
Salaheddin Hosseinzadeh 2014년 3월 13일
Is there a problem with this code? If there is then let us know about it plz, I don't have the beloved MATLAB to run this code ATM!

댓글을 달려면 로그인하십시오.

답변 (0개)

카테고리

Help CenterFile Exchange에서 Logical에 대해 자세히 알아보기

태그

제품

Community Treasure Hunt

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

Start Hunting!

Translated by