whu 1473 - Check the Identity 乱搞

乱搞.

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<cmath>
#include<stack>
using namespace std;

const double Pi = acos(-1);
const double eps = 1e-8;
char str[310][10];
int n, m;
int sign(double x){
    return x<-eps?-1:(x>eps);
}
stack<double> Q;
double work( double x ){
    while( !Q.empty() ) Q.pop();
    Q.push(x);
    for(int i = 0; i < n; i++){
        switch( str[i][0] ){
            case 's':{
                double t = Q.top();Q.pop();//if( sign(t-Pi/2) == 0 ) return 1; 
                Q.push( sin(t) ); break;}
            case 'c':{
                double t = Q.top();Q.pop();//if( sign(t-Pi/2) == 0 ) return 1; 
                Q.push( cos(t) ); break;}
            case 't':{
                double t = Q.top();Q.pop();//if( sign(t-Pi/2) == 0 ) return 1;  
                Q.push( tan(t) ); break;}
            case '+':{
                double a = Q.top();Q.pop();//if( sign(a-Pi/2) == 0 ) return 1; 
                double b = Q.top();Q.pop();//if( sign(b-Pi/2) == 0 ) return 1; 
                Q.push(b+a); break; }
            case '-':{
                double a = Q.top();Q.pop();//if( sign(a-Pi/2) == 0 ) return 1; 
                double b = Q.top();Q.pop();//if( sign(b-Pi/2) == 0 ) return 1; 
                Q.push(b-a); break; }
            case '*':{
                double a = Q.top();Q.pop();//if( sign(a-Pi/2) == 0 ) return 1; 
                double b = Q.top();Q.pop();//if( sign(b-Pi/2) == 0 ) return 1; 
                Q.push(b*a); break; }
            default:
                Q.push(x);
        }    
    }
    return Q.top();
}
int main(){
    int T;
    scanf("%d",&T);
    for(int Case = 1; Case <= T; Case++){
        scanf("%d", &n);
        bool flag = false;
        for(int i = 0; i < n; i++){
            scanf("%s", str[i] );
            if( str[i][0] == '-' ) flag = true;
        }
        printf("Case %d: ", Case );
    //    if( flag == false ){ puts("No"); continue; } //不存在减法则必定不会为0 
        int num = 0;
        for(int i = 0; i < 100; i++){
            double x = (rand()%100)/100.*Pi/2.;   //此处很神奇，模1000必WA 
            if( sign( work(x) ) == 0 ) num++;
        }    
        if( sign( 1.*num/100. - 0.8 ) >= 0 ) puts("Yes");
        else    puts("No");
    }
    return 0;    
}