C程序: Convert string of chars representing numbers to ints

Question

我正在学习 C，我正在尝试让一个玩具示例工作。我的假用例给出了一个字符字符串，其中每个字符代表一个 int，循环遍历该字符串的每个字符并将其转换为 int。到目前为止我尝试过的方法都没有成功。

编辑:原始问题经过编辑，现在包含一个 main() ，以允许响应者根据评论中的建议编译和使用 strtol 。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main(int argc, char **argv) {
  char *charNums = "12345";
  int num, num2, num3, i, n = strlen(charNums);
  char *ptr = charNums;

  for (i = 0; i < n; i++) {
    num = atoi(&charNums[i]);
    num2 = atoi(ptr);
    num3 = strtol(ptr, NULL, 10);
    printf("\ncharNums[%d] = %c (the expected value but as an int not a char)\n num = %d\n num2 = %d\n num3 = %d\n", 
        i, charNums[i], num, num2, num3);
    ptr++;
  }
  return 0;
)

编辑:显示C代码的编译方法以及程序执行

gcc -o soQuestion main.c
./soQuestion
charNums[0] = 1 (the expected value but as an int not a char)
  num = 12345
  num2 = 12345
  num3 = 12345

charNums[1] = 2 (the expected value but as an int not a char)
  num = 2345
  num2 = 2345
  num3 = 2345

charNums[2] = 3 (the expected value but as an int not a char)
  num = 345
  num2 = 345
  num3 = 345

charNums[3] = 4 (the expected value but as an int not a char)
  num = 45
  num2 = 45
  num3 = 45

charNums[4] = 5 (the expected value but as an int not a char)
  num = 5
  num2 = 5
  num3 = 5

感谢任何反馈。

编辑:该程序的预期结果是将字符串“12345”中的每个字符转换为 1 2 3 4 5 的单个整数，以便我可以对它们进行数学运算，例如对它们求和1 + 2 + 3 + 4 + 5 = 15

Answer 1

在执行 subtraction 时，您可以将字符视为数字这样:

int diff = c - '0';  //c is a character. 
//Avoid using hard code values like 48 in place of '0'.
//as they less readable.

那么diff什么也不是，只是积分值。