﻿ 为什么(int)55 == 54在C？ - 代码日志

#### 为什么(int)55 == 54在C？

``````// 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));
}
``````

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

55,54,0

http://stackoverflow.com/questions/553974/why-does-int55-54-in-c