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  • 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;    
    }
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  • 原文地址:https://www.cnblogs.com/yefeng1627/p/3036641.html
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