%g 如何对浮点数进行四舍五入？
当我在 printf() 中使用 %g 作为格式说明符时，有时它会向上舍入到小数点后 2 位，有时向上舍入到 3 位，有时向上舍入到 4 位。 ..它是如何做到的？
实际上，对于浮点数，我们应该在哪里使用 %g 而不是 %f 或 %e 呢？
While I'm using %g as format specifier in printf(), sometimes it rounds up upto 2 places after decimal point, sometimes upto 3 places , someimes upto 4 places...how it does so?
Actually where we should use %g instead of %f or %e for floating point numbers?
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%g格式说明符的舍入方式与%f类似，但如果%f会产生4.234000，则%g将省略尾随零并打印4.234。当某些数字打印为
12345.6，而稍大的数字将打印为1.235 时，应使用。%ge04The
%gformat specifier does its rounding just like%fwould do, but if%fwould result in4.234000, then%gwill omit the trailing zeros and print4.234.%gshould be used when it makes the most sense in your output format that some numbers are printed as12345.6, while a slightly bigger number would be printed as1.235e04.%g根据值自动在使用%e和%f之间“翻转”，以尝试显示尽可能多的信息，与手持计算器的操作方式相同。此外，
%g不包括尾随零和小数点。%gautomatically 'flips' between using%eand%fdepending on the value, in an attempt to display as much information as possible, in the same way as hand-held calculators do.Also, with
%gtrailing zeroes and decimal point are not included.对于
%f转换，“精度”是小数点后的位数，而对于%g则是小数点后的位数。 有效数字。两种情况下的默认精度均为 6。
For the
%fconversion, the “precision” is the number of digits after the decimal point, while for%git is the number of significant digits.The default precision is 6 in both cases.
来自 printf 手册：
“双参数以 f 或 e（或 F或 E 代表
G 转换）。精度指定有效位数。如果精度缺失，则给出6位；
如果精度为零，则视为1。使用样式e
如果转换后的指数小于 -4 或更大
大于或等于精度。尾随零被删除
结果的小数部分；只出现小数点
如果它后面至少跟着一位数字。”
我的意思不是“RTFM”，但您可能会在手册中有关控制精度和长度的部分中找到所需的内容。
From the printf manual:
"The double argument is converted in style f or e (or F or E for
G conversions). The precision specifies the number of significant digits. If the precision is missing, 6 digits are given;
if the precision is zero, it is treated as 1. Style e is used
if the exponent from its conversion is less than -4 or greater
than or equal to the precision. Trailing zeros are removed from
the fractional part of the result; a decimal point appears only
if it is followed by at least one digit."
I don't mean to "RTFM", but you'll probably find what you're looking for in the manual sections on controlling precision and length.