[英]Function is not returning anything in C
I am trying to return a string in a C program.我试图在 C 程序中返回一个字符串。 The program is a roman numeral encoder and takes and integer and returns a string as roman numerals:该程序是一个罗马数字编码器,接受 integer 并返回一个罗马数字字符串:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char *solution(int n);
int main() {
printf("%s", solution(2253));
return 0;
}
char *solution(int n) {
char res[] = "";
char *resPtr = res;
while(n != 0)
{
if (n >= 1000)
{
strncat(res, "M", 1);
n -= 1000;
}
...
}
return resPtr;
}
The pointer is not returning anything指针不返回任何东西
Two issues:两个问题:
Example:例子:
#include <stdint.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
const char *hundreds[] = {"C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM" };
const char *tens[] = {"X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC", };
const char *digits[] = {"I","II","III","IV","V","VI","VII","VIII","IX"};
char *solution(int n);
int main()
{
char *p;
printf("%s", p = solution(2253));
free(p);
return 0;
}
char *solution(int n)
{
char *resPtr = malloc(n / 1000 + 4 + 4 + 4 + 1);
size_t pos = 0;
if(resPtr)
{
while(n >= 1000)
{
resPtr[pos++] = 'M'; // no need of expensive strncat function
n -= 1000;
}
if(n / 100)
{
strcpy(&resPtr[pos], hundreds[n / 100 - 1]);
pos += strlen(hundreds[n / 100 - 1]);
n = n % 100;
}
if(n / 10)
{
strcpy(&resPtr[pos], tens[n / 10 - 1]);
pos += strlen(tens[n / 10 - 1]);
}
n = n % 10;
if(n) strcpy(&resPtr[pos], digits[n - 1]);
}
return resPtr;
}
char res[]
is local variable to the function and it goes out of scope after you exit your function. char res[]
是 function 的局部变量,退出 function 后它会从 scope 中消失。
use strcpy instead, use a bigger string (you can go for dynamic memory allocation)改为使用 strcpy,使用更大的字符串(您可以使用 go 进行动态 memory 分配)
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