TYVJ P1042 [表达式计算3]

最新推荐文章于 2016-08-12 19:40:25 发布

转载最新推荐文章于 2016-08-12 19:40:25 发布 · 138 阅读

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原文链接：http://www.cnblogs.com/FreeDestiny/archive/2011/10/25/2223303.html

本文详细介绍了一种使用Pascal语言处理字符串表达式的算法，包括加、减、乘、除和幂运算。通过一系列函数实现了对字符串表达式的解析和计算，如乘法、加法、减法、除法和幂运算的处理过程。

最近做的字符串处理问题比较多，所以这个题目直接用的字符串来处理，不需要高精，只需要注意细节。

[pascal 代码]

VAR
        s,pre:string;
        cz:boolean;
        i:longint;
Procedure init;
 begin
        readln(s);
 end;
Function ysf(ch:char):boolean;
 begin
        ysf:=false;
        if ch='+' then exit(true);
        if ch='-' then exit(true);
        if ch='*' then exit(true);
        if ch='/' then exit(true);
        if ch='^' then exit(true);
 end;
Function cheng(s1,s2:string):string;
 var
        a,b,c:longint;
 begin
        val(s1,a);
        val(s2,b);
        c:=a*b;
        str(c,cheng);
 end;
Function jia(s1,s2:string):string;
 var
        a,b,c:longint;
 begin
        val(s1,a);
        val(s2,b);
        c:=a+b;
        str(c,jia);
 end;
Function jian(s1,s2:string):string;
var
        a,b,c:longint;
 begin
        val(s1,a);
        val(s2,b);
        c:=a-b;
        str(c,jian);
 end;
Function chu(s1,s2:string):string;
 var
        a,b,c:longint;
 begin
        val(s1,a);
        val(s2,b);
        c:=a div b;
        str(c,chu);
 end;
Function cf(s1,s2:string):string;
 var
        a,b,c:longint;
        i:longint;
 begin
        val(s1,a);
        val(s2,b);
        c:=1;
        for i:=1 to b do c:=c*a;
        str(c,cf);
 end;
Procedure handlecf;
 var
        i,j,l,r,t:longint;
        s1,s2,pre:string;
 begin
        while true do
                begin
                        for i:=1 to length(s) do if s[i]='^' then break;
                        if i=length(s) then exit;
                        for j:=i-1 downto 1 do if ysf(s[j]) then break;
                        l:=j;
                        if j<>1 then inc(l);
                        for j:=i+1 to length(s) do if ysf(s[j]) then break;
                        r:=j;
                        if j<>length(s) then dec(r);
                        s1:=copy(s,l,i-l);
                        s2:=copy(s,i+1,r-i);
                        delete(s,l,r-l+1);
                        pre:=cf(s1,s2);
                        insert(pre,s,l);
                end;
 end;
Procedure handlechu;
 var
        i,j,l,r,t:longint;
        s1,s2,pre:string;
 begin
        while true do
                begin
                        for i:=1 to length(s) do if s[i]='/' then break;
                        if i=length(s) then exit;
                        for j:=i-1 downto 1 do if ysf(s[j]) then break;
                        l:=j;
                        if j<>1 then inc(l);
                        for j:=i+1 to length(s) do if ysf(s[j]) then break;
                        r:=j;
                        if j<>length(s) then dec(r);
                        s1:=copy(s,l,i-l);
                        s2:=copy(s,i+1,r-i);
                        delete(s,l,r-l+1);
                        pre:=chu(s1,s2);
                        insert(pre,s,l);
                        //writeln(s);
                end;
 end;
Procedure handlecheng;
 var
        i,j,l,r,t:longint;
        s1,s2,pre:string;
 begin
        while true do
                begin
                        for i:=1 to length(s) do if s[i]='*' then break;
                        if i=length(s) then exit;
                        for j:=i-1 downto 1 do if ysf(s[j]) then break;
                        l:=j;
                        if j<>1 then inc(l);
                        for j:=i+1 to length(s) do if ysf(s[j]) then break;
                        r:=j;
                        if j<>length(s) then dec(r);
                        s1:=copy(s,l,i-l);
                        s2:=copy(s,i+1,r-i);
                        delete(s,l,r-l+1);
                        pre:=cheng(s1,s2);
                        insert(pre,s,l);
                end;
 end;
Procedure handlejia;
 var
        i,j,l,r,t:longint;
        s1,s2,pre:string;
 begin
        while true do
                begin
                        for i:=1 to length(s) do if s[i]='+' then break;
                        if i=length(s) then exit;
                        for j:=i-1 downto 1 do if ysf(s[j]) then break;
                        l:=j;
                        if j<>1 then inc(l);
                        for j:=i+1 to length(s) do if ysf(s[j]) then break;
                        r:=j;
                        if j<>length(s) then dec(r);
                        s1:=copy(s,l,i-l);
                        s2:=copy(s,i+1,r-i);
                        delete(s,l,r-l+1);
                        pre:=jia(s1,s2);
                        insert(pre,s,l);
                end;
 end;
Procedure handlejian;
 var
        i,j,l,r,t:longint;
        s1,s2,pre:string;
 begin
        while true do
                begin
                        for i:=1 to length(s) do if s[i]='-' then break;
                        if i=length(s) then exit;
                        for j:=i-1 downto 1 do if ysf(s[j]) then break;
                        l:=j;
                        if j<>1 then inc(l);
                        for j:=i+1 to length(s) do if ysf(s[j]) then break;
                        r:=j;
                        if j<>length(s) then dec(r);
                        s1:=copy(s,l,i-l);
                        s2:=copy(s,i+1,r-i);
                        delete(s,l,r-l+1);
                        pre:=jian(s1,s2);
                        insert(pre,s,l);
                end;
 end;
Begin
        init;
        handlecf;
        handlechu;
        handlecheng;
        handlejian;
        handlejia;
        {cz:=false;
        for i:=1 to length(s) do if s[i]<>'0' then cz:=true;
        if not cz then writeln('0') else} 
        writeln(s);
End.

转载于:https://www.cnblogs.com/FreeDestiny/archive/2011/10/25/2223303.html