QA0007

clear all;close all;clc

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%% generate random x
N=12;                 % define length vector x
n10=2;               % make sure at least n0 zeros in vector
n20=6;               % define roof amount zeros in x
N0=randi([n10 n20],1,1);   % define amount zeros in x
disp([num2str(N0) ' zeros'])
x1=randi([-9 9],1,N-N0)

x=[]
N1=N-N0
N01=N0
while N1+N01>0
    if ~randi([0 1],1,1) && N01>0  % decide 0 or ~0
        x=[x 0];               % append 0
        N01=N01-1;
    end
    if ~randi([0 1],1,1) && N1>0
        x=[x x1(1)];
        x1(1)=[];
        N1=N1-1;
    end
end
x % check

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%% find largest number next to null
L=[]
nL0=find(x==0)
for k=1:1:numel(nL0)
    if (nL0(k)>1 && ...
        nL0(k)<N && ...
        x(nL0(k)+1))
        L=[L x(nL0(k)+1)]; 
    end
      if (nL0(k)>1 && ...
          nL0(k)<N && ...
          x(nL0(k)-1))
          L=[L x(nL0(k)-1)]; 
      end
       
    if (~x(1)==1 && x(2))
        L=[L x(2)];
    end
    
       if (~x(N) && x(N-1))
        L=[L x(N-1)];
    end
end

max(L)

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%% comments on a few other answers 
%%
    % Naixin mu answer doesn't work for
    % x=[0     9     0     6     0     5     6     8     5     2     5]
    % should return 9 but returns 6

x2=[-inf,x,-inf];
a=x(find(x2==0)-1);
b=x(find(x2==0)+1);
y=max([a,b])

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%%
% Haoyu Dai answer doesn't work for 
    % x=[0     9     0     6     0     5     6     8     5     2     5]
    % should return 9 but returns a vector with 5 elements
    % one of them is the correct answer, but when asked for max
    % there's only one possible answer.
    
y = [];
a=[];
k=1;
L2=length(x);
for i=1:L2
if x(i)==0
if i==1
a(k)=x(i+1);
k=k+1;
elseif i==L2
a(k)=x(i-1);
k=k+1;
else
a(k)=x(i-1);
a(k+1)=x(i+1);
k=k+2;
end
end
end
[y,index]=max(a);

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%%
% Jianghao Su answer doesn't work for 
   % x=  [0    -2    -4     0    -7    -2     0     0    -2    -7     0]
% it returns 0

x=[-inf,x,-inf];
zeroindex=find(~x);
zeroindexl=zeroindex-1;
zeroindexr=zeroindex+1;
y=max([x(zeroindexl),x(zeroindexr)])

​

%%
% Quinhua Ye answer doesn't work
% because for % x=  [0    -2    -4     0    -7    -2     0     0    -2    -7     0]
% it returns error: index exceeds array elements number (12)
% attempting to index beyond available indices.

x2 = [min(x(x~=0)),x,min(x(x~=0))];
indx = find(x2 == 0);
y = max([x(indx-1),x(indx+1)]);