linux C不用庫函數實現字符串轉數字

1.計算字符串長度；
2.計算10的n次方；

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

int get_power(int n)
{
	int i =0 ;
	int sum = 10;
	if (n == 0)
	{
		return 1;
	}
	for (i = 1; i<n; i++)
	{
		sum *= 10;
	}
	return sum;
}
int get_str_len(char *p)
{
	int len = 0;
	while(*p++ !='\0')
	{
		len++;
	}
	return len;
}
int main()
{
	char szBuff[]="1123432";
	int len = 0;
	int i = 0;
	int tmp = 0;
	int power_value = 0;
	int sum = 0;
	len = get_str_len(szBuff);
	for (i = 0; i<len; i++) 
	{
		tmp = szBuff[i]-48;
		power_value = get_power(len-i-1);
		sum += tmp*power_value;
		printf("i=%d, tmp=%d, power_value=%d, sum=%d\n", i, tmp, power_value, sum);
	}

	printf("%d\n", sum);
	return 0;
}

結果：
i=0, tmp=1, power_value=1000000, sum=1000000
i=1, tmp=1, power_value=100000, sum=1100000
i=2, tmp=2, power_value=10000, sum=1120000
i=3, tmp=3, power_value=1000, sum=1123000
i=4, tmp=4, power_value=100, sum=1123400
i=5, tmp=3, power_value=10, sum=1123430
i=6, tmp=2, power_value=1, sum=1123432
1123432
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