第1条题解

这一道题并不难代码如下。

#include <iostream> 
#include <iomanip> 
#include <cmath> 
#include <vector> 
#include <algorithm>  
using namespace std;  
double f(double a, double b, double c, double d, double x) { 
    return a * x * x * x + b * x * x + c * x + d; 
} 
double findRoot(double a, double b, double c, double d, double left, double right) { 
    double mid; 
    while (right - left > 1e-5) { 
        mid = (left + right) / 2; 
        if (f(a, b, c, d, mid) * f(a, b, c, d, left) < 0) { 
            right = mid; 
        } else { 
            left = mid; 
        } 
    } 
    return mid; 
}  
int main() { 
    double a, b, c, d; 
    cin >> a >> b >> c >> d;  
    vector<double> roots;  
    for (int i = -100; i <= 100; ++i) { 
        double left = i; 
        double right = i + 1; 
        if (f(a, b, c, d, left) == 0) { 
            roots.push_back(left);  
        } else if (f(a, b, c, d, left) * f(a, b, c, d, right) < 0) { 
            roots.push_back(findRoot(a,  b, c, d, left, right)); 
        } 
    }  
    sort(roots.begin(),  roots.end());  
    for (int i = 0; i < roots.size();  ++i) { 
        cout << fixed << setprecision(2) << roots[i]; 
        if (i < roots.size()  - 1) { 
            cout << " "; 
        } 
    } 
    cout << endl; 
 
    return 0; 
}

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