Find 2012 - ELP

% Find 2012
% Written by Eric L. Pheterson
% February 18, 2012
%
% The original purpose of the following function was to find the year 2012
% using 3 operators (+,-,/,*) and the digits 1-9 in order. Now it handles
% any year, with any amount of operators. For example 12+34*56+78+9 = 2003
% Written in MatLab.
%
% Example Output
%                             ...
% 12-3456/7*89 =  -4.39e+04 | 3159
% 12-34*5678-9 =    -193049 | 3160
% 1/2/34567+89 =   8.90e+01 | 3161
% 1234-5-6+789 =       2012 | 3162
% Elapsed time is 21.883291 seconds.

function find2012()
tic

% What are we finding today?
year=2012;
ops=3; %number of operators (+,-,/,*) must be <= 9

% Prepare
size=9+ops;
tries=0;
guess=0;

while(guess~=year)
    % Prepare
    k9 = zeros(size+2,1); % First and last always 0
    i=2; % First location to place numbers
    placed = 0;
    location = rand_int(2,size,1);
    eq='';

    % Place the operators
    while(placed < ops)
        % Choose an operator (-1 /, -2 *, -3 +, -4 -)
        operator = rand_int(-4,-1,1);
        while((k9(location)~=0)||(k9(location-1)<0)|| ...
                (k9(location+1)<0)||(location==2&&operator>-4))
            % Choose a location
            location = rand_int(2,size,1);
        end
        k9(location)=operator;
        placed=placed+1;
    end
    placed = 0;

    % Fill the remaining places
    while(i<size+2)
        if(k9(i)<0)
            i=i+1;
        else
            placed=placed+1;
            k9(i)=placed;
            i=i+1;
        end
    end
    i=2;

    % Construct the string
    while(i<size+2)
        if(k9(i)>0)
            eq = strcat(eq,int2str(k9(i)));
        elseif(k9(i)==-1)
            eq = strcat(eq,'/');
        elseif(k9(i)==-2)
            eq = strcat(eq,'*');
        elseif(k9(i)==-3)
            eq = strcat(eq,'+');
        elseif(k9(i)==-4)
            eq = strcat(eq,'-');
        end
        i = i+1;
    end

    % Cross your fingers!
    guess=eval(eq);
    tries=tries+1;
    fprintf('%s = %10.2d | %i\n',eq,guess,tries)
end
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