[HNOI2002]沙漠寻宝 题解

一道大模拟

代码

#include <cstdio>
#include <iostream>
#include <cstring>
#include <string>
using namespace std;

string st[1010];
int value[26];
int f,o,s,i;
int p[1010],num[1010];
int s1[150];
char s2[150];
int t1=0,t2=0;
char c;

bool check(char ch){
    if((ch>='a'&&ch<='z')||(ch>='0'&&ch<='9')||(ch=='+')||(ch=='-')||(ch=='*')
        ||(ch=='/')||(ch=='(')||(ch==')')||(ch=='='))
        return true;
    return false;
}

void calcu(){
    int x1,x2,x;
    char p;
    p=s2[t2--];
    x2=s1[t1--];
    x1=s1[t1--];
    switch(p){
        case '+' : x=x1+x2; break;
        case '-' : x=x1-x2; break;
        case '*' : x=x1*x2; break;
        case '/' : x=x1/x2; break;
    }
    s1[++t1]=x;
}

void readStr(){
    char b;
    s++;
    int count=0;
    scanf("%c",&b);
    while(!check(b)) scanf("%c",&b);
    while(check(b)){
        st[s]=st[s]+b;
        if(b=='d')count++;
        if(count>20){
        	st[s]=st[s].substr(0,3);
        	break;
        }
        scanf("%c",&b);
    }
}

int result(string t){
    char c;
    unsigned i=0;
    t1=0,t2=0;
    int v;
    while(i<t.size()){
        c=t[i];
        if(c=='+'||c=='-'){
            while(t2&&s2[t2]!='(') calcu();
            s2[++t2]=c;
            i++;
        }
        else if(c=='*'||c=='/'){
            while(t2&&(s2[t2]=='*' || s2[t2]=='/')) calcu();
            s2[++t2]=c;
            i++;
        }
        else if(c=='('){
            s2[++t2]=c;
            i++;
        }
        else if(c==')'){
            while(s2[t2]!='(') calcu();
            t2--;
            i++;
        }
        else if(c>='a'&&c<='z'){
            s1[++t1]=value[c-'a'];
            i++;
        }else{
            v=0;
            do{
                v=10*v+c-'0';
                c=t[++i];
            }while(c>='0'&&c<='9'&&i<t.size());
            s1[++t1]=v;
        }
    }
    while(t2) calcu();
    return s1[t1];
}

int main(){
    o=1;
    while(o!=0){
        readStr();
        //cout<<st[s]<<endl;
        if(st[s]=="loop") o++;
        else if(st[s]=="end") o--;
    }
    i=2;
    f=1;num[1]=1;
    while(i<=s){
        if(st[i]=="loop"){
            f++;
            i++;
            num[f]=result(st[i]);
            i++; p[f]=i;
        }
        else if(st[i]=="end"){
            num[f]--;
            if(num[f]==0){
                f--;i++;
            }else i=p[f];
        }
        else if(st[i]=="break"){
            o=1;
            while(o!=0){
                i++;
                if(st[i]=="loop") o++;
                else if(st[i]=="end") o--;
            }
            num[f]=1;
        }else if(st[i]=="continue"){
            o=1;
            while(o!=0){
                i++;
                if(st[i]=="loop") o++;
                else if(st[i]=="end") o--;
            }
        }
        else if(st[i]=="write"){
            i++;
            printf("%d\n",result(st[i]));
            i++;
        }
        else{
            value[st[i][0]-'a']=result(st[i].substr(2,st[i].size()-2));
            i++;
        }
    }
    return 0;
}