为什么(int)55 == 54在C?

所以我正在学习C。我有我的“C编程语言”和“有效C”出来,我正在通过项目欧拉。问题1 … dunzo问题2 …不是那么多我在VS2008在Win32控制台应用程序上工作。

斐波那契序列的所有偶数的总和在400万以下?

它不工作,所以我削减到100的测试用例…

这是我写的…

// Problem2.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
using namespace std;

int _tmain(int argc, _TCHAR* argv[])
{
    cout << "Project Euler Problem 2:\n\n";
    cout << "Each new term in the Fibonacci sequence is generated by adding the previous two terms. By starting with 1 and 2, the first 10 terms will be:\n\n";
    cout << "1, 2, 3, 5, 8, 13, 21, 34, 55, 89, ...\n\n";
    cout << "Find the sum of all the even-valued terms in the sequence which do not exceed four million.\n\n";
    cout << "Answer:  " << Solve();
}

double Solve() {
    int FibIndex = 0;
    double result = 0.0;
    double currentFib = GenerateNthFibonacciNumber(FibIndex);
    while (currentFib < 100.0){
        cout << currentFib << " " << (int)currentFib << " " << (int)currentFib % 2 << "\n";
        if ((int)currentFib % 2 == 0){
            result += currentFib;
            cout<<(int)currentFib;
        }
        currentFib = GenerateNthFibonacciNumber(++FibIndex);
    }
    return result;
}

double GenerateNthFibonacciNumber(const int n){
    //This generates the nth Fibonacci Number using Binet's Formula
    const double PHI = (1.0 + sqrt(5.0)) / 2.0;
    return ((pow(PHI,n)-pow(-1.0/PHI,n)) / sqrt(5.0));
}

这里是输出…

Project Euler Problem 2:

Each new term in the Fibonacci
sequence is generated by adding the
previous two terms. By starting with 1
and 2, the first 10 terms will be:

1, 2, 3, 5, 8, 13, 21, 34, 55, 89, …

Find the sum of all the even-valued
terms in the sequence which do not
exceed four million.

0 0 0
1 1 1
1 1 1
2 2
0
3 3 1
5 5 1
8 8 0
13
13 1
21 21 1
34 34 0
55 54
0
89 89 1
Answer: 99

所以我有三列调试代码…从生成函数返回的数字,(int)generatedNumber和(int)generatedNumber%2

所以在第十一届我们有

55,54,0

为什么(int)55 = 54?

谢谢

转换为int可以截断数字,就像调用floor(currentFib)一样。所以即使currentFib是54.999999 …(一个数字如此接近55,它将在打印时被舍入),(int)currentFib将产生54。
翻译自:https://stackoverflow.com/questions/553974/why-does-int55-54-in-c

转载注明原文:为什么(int)55 == 54在C?