[C++知识库]C语言实现数字字符转换为整型数字

1.常见的解决方案
知识点备注: ‘1’ - ‘0’ = 1
具体事例分析:

char str[10] = “12345”;
‘1’ - ‘0’ = 1;
1 * 10 + ‘2’ - ‘0’ = 12;
12 * 10 + ‘3’ - ‘0’ = 123;
123 * 10 + ‘4’ - ‘0’ = 1234;
1234 * 10 + ‘5’ - ‘0’ = 12345;

身份证检验案例：

 #include<stdio.h>

int main(){
	char idArray[18]; // 存储身份证前18位id 
	printf("input your id：");
	gets(idArray);   // 接收输入的身份证信息
	
	int ratioId[17] = {7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2};
	char check[11] = {'1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2'};
	
	int i, sum = 0;
	for(i = 0; i < 17; i++){
		sum += (idArray[i] - '0')*ratioId[i];    //对前17位数字加权求和，这里的idArray[i] - '0'实现的是数字字符向整型数字的转变
	}
	
	if(idArray[17] == check[sum % 11]){
		printf("身份证合法~");
	} else{
		printf("身份证不合法~");
	}
	return 0;
}

实验结果：