c - 去掉C中 float 的无用0

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如何删除不影响数值的零

 float X1 = (-b + sqrt(pow(b,2) - (4*a*c)))/(2*a);

有时，如果 X1 是一个不带小数的数字，它将是 X1=4.0000我怎样才能避免这种情况

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Answer 1

选项#1

使用printf的%g

Unless alternative representation is requested the trailing zeros are removed, also the decimal point character is removed if no fractional part is left.

代码示例:

double x = 4.0;
printf("DEBUG:%f\n", x);
printf("X1=%g\n", x);

输出:

DEBUG:4.000000
X1=4

选项#2

将其输出到字符串并进行处理。

代码示例:

double x = 4.0;
char buff[48];
int len;
len = snprintf(buff, sizeof buff, "%.4f", x);
printf("DEBUG:%s\n", buff);
char *p = buff + len -1;
while(*p == '0'){
    *p-- = 0;
}
if(*p == '.')
    *p = 0;
printf("X1=%s\n", buff);

输出:

DEBUG:4.0000
X1=4