[C++]C++四舍五入保留到n位小数
#include <sstream>
#include <iostream>
#include <iomanip>
using namespace std;
/**
* 四舍五入保留到n位小数
* @param number
* @param bits
* @return
*/
static double round_1(double number, unsigned int bits) {
stringstream ss;
ss << fixed << setprecision(bits) << number;
ss >> number;
return number;
}
typedef long long LL;
/**
* 四舍五入保留到n位小数
* @param number
* @param bits
* @return
*/
static double round_2(double number, unsigned int bits) {
LL integerPart = number;
number -= integerPart;
for (unsigned int i = 0; i < bits; ++i)
number *= 10;
number = (LL) (number + 0.5);
for (unsigned int i = 0; i < bits; ++i)
number /= 10;
return integerPart + number;
}
int main() {
double pi = 3.1415926;
double r_pi1 = round_1(pi, 3);
double r_pi2 = round_2(pi, 4);
cout << "pi=" << pi << endl;
cout << "r_pi1=" << r_pi1 << endl;
cout << "r_pi2=" << r_pi2 << endl;
}
运行结果
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