whu 1473 - Check the Identity 乱搞-优快云博客

本文介绍了一个使用C++实现的数学函数计算器程序，该程序能够通过栈结构解析并计算一系列包括正弦、余弦、正切等在内的三角函数表达式。通过输入不同的函数组合，程序能够返回计算结果，并且通过随机数生成不同角度的输入来测试特定条件下是否能求得零值。

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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;    
}