实现逆波兰式与递归计算代码,Perl代码库,德仔网

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【Perl】实现逆波兰式与递归计算
作者:两把刷子 / 发布于2014/1/17/ 818
#!/usr/bin/perl

usestrict;

usewarnings;

useData::Dumper;

while(1){

my$data=&get_input();

if(!$data){

print"your expr is illegal,please check it\n";next;

}

my@tree=&get_tree($data);

print"The tree is: \n", Dumper(@tree)," \n";

my$result=&count($tree[0]);

print"The result of the expr is: $result\n";

}

######获得输入数据函数

subget_input{

print"Input your expr>>";

chomp(my$inputdata=<STDIN>);

$inputdata=~s/\s//g;#去除所有的空白符

if(!$inputdata){exit;}

if($inputdata=~/[a-zA-Z\.]/) {#做简单检查是否存在小数或者字符出现

return0;}

$inputdata=join("",$inputdata,"#")if(substr($inputdata,length($inputdata)-1,1) ne"#"); #在最后补#

}

#get the tree of the expr

subget_tree{

my$data=pop;

my($stop,$top,$ch,@stack,@tree);

$top=0;$stack[0]='#';

while($top<length($data)){

$ch=substr($data,$top,1);

if($cheq"+"or$cheq"-"){

my$op=pop(@stack);

if($opeq'#'or$opeq'('or$opeq'['or$opeq'{'){

push(@stack,$op);push(@stack,$ch);}

else{

push(@stack,$op);

while(1){

my$op=pop(@stack);

if($opeq'#'or$opeq'('or$opeq'['or$opeq'{'){

push(@stack,$op);push(@stack,$ch);last;}

else{

my@node;

push(@node,$op);push(@node,pop(@tree));

push(@node,pop(@tree));push(@tree,[@node]);

}

}

}

$top=$top+1;next;

}

if($cheq"*"or$cheq"/")

{

my$op=pop(@stack);

if($opne"*"and$opne"/"){

push(@stack,$op);push(@stack,$ch);}

else{

push(@stack,$op);

while(1){

my$op=pop(@stack);

if($opne"*"and$opne"/"){

push(@stack,$op);push(@stack,$ch);last;}

else{

my@node;

push(@node,$op);push(@node,pop(@tree));

push(@node,pop(@tree));push(@tree,[@node]);

}

}

}

$top=$top+1;next;

}

if($cheq'('or$cheq'{'or$cheq'['){

push(@stack,$ch);$top=$top+1;next;

}

if($cheq')'or$cheq']'or$cheq'}'){

while(1){

my$op=pop(@stack);

if($opeq'('or$opeq'['or$opeq'{'){

last;}

my@node;

push(@node,$op);push(@node,pop(@tree));

push(@node,pop(@tree));push(@tree,[@node])

}

$top=$top+1;next;

}

if($cheq'#'){

while(1){

my$op=pop(@stack);

if($opeq'#'){

last;}

else{

my@node;

push(@node,$op);push(@node,pop(@tree));

push(@node,pop(@tree));push(@tree,[@node]);

}

}

$top=$top+1;next;

}

if($chge'0'and$chle'9'){

my$num=0;

while($chge'0'and$chle'9'){

$num=$num*10+$ch;$top=$top+1;

$ch=substr($data,$top,1);

}

push(@tree,$num);next;

}

else{

$top=$top+1;

}

}

returnreverse@tree;

}



#####检查是否为引用

subjudge_digit

{

my$data=shift;

if(ref($data) eq"ARRAY"){

return0;}

else{

return1;}

}

#####根据树计算最终结果

########利用递归函数实现

subcount

{

my$x=shift;

my@data=@{$x};

if(judge_digit($data[1])==0){

$data[1]=count($data[1]);

}

if(judge_digit($data[2])==0){

$data[2]=count($data[2]);

}

if($data[0] eq"+"){

return$data[1]+$data[2];

}elsif($data[0] eq"-") {

return$data[2]-$data[1];

}elsif($data[0] eq"*"){

return$data[1]*$data[2];

}elsif($data[0] eq"/") {

return$data[2]/$data[1];

}

}
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