charArrayToInt + intLength

stdlib中自带str与int/long之间的互转：

itoa、ltoa(int, char*, int)

strtoi、strtol(char*, char**, int)

---

关于scanf读取数据的问题：

  1 #include 
  2 
  3 int main(){
  4     char data[15] = "hello,world!";
  5     printf("%s\n",data);
  6     scanf("%s",data);
  7     printf("%s\n",data);
  8     int i;
  9     for(i=0;i<15;i++){
 10         printf("%c ",data[i]);
 11     }
 12     if(data[3]=='\0'){
 13         printf("hello\n");
 14     }
 15     if(data[3]=='\n'){
 16         printf("hello\n");
 17     }
 18 
 19 
 20     printf("%d--%d\n",'\0','\n');
 21 
 22     return 0;
 23 }

/*
hello,world!
acd
acd
a c d  o , w o r l d !    hello
0--10
*/

☞ 模拟stdlib.h中strtoi(char*,char**,redix)/strtol(char*,char**,redix)：

#include 

int charArrayToInt(char* data){
    if(data==NULL){
        return -1;
    }
    int length = 0;
    while(data[length]!='\0'){
        length++;
    }
    int i = 0;
    int j = 0;
    for(;i='0'){}else{
            return -1; 
        }
    }   
    int res = 0;
    for(i=0;i

---

☞ 将int类型转换为字符串：sprintf

int intLength(int num){
    char buff[15];
    sprintf(buff,"%d",num);
    int length = 0;
    while(buff[length]!='\0'){
        length++;
    }
    return length;
}

---

---

检测字符串是否为指定长度数字：

#include 

/*
  成功返回实际值
  失败：
    -1:不能以0开头
    -2:格式有误
    -3:长度错误
 */
int check(char *data,int len){
    if(data==NULL){
        return -1; 
    }   
    int length=0;
    while(data[length]!='\0'){
        length++;
    }   
    int i=0;
    int j=0;
    if(data[0]==0){
        return -1; 
    }   
    for(;i='0'){}else{
            return -2; 
        }
    }   
    // 长度判断
    if(length!=len){
        return -3; 
    }   
    return 0;
}

// 测试
int main(){
    char *data1 = "a123";
    char *data2 = "1a23";
    char *data3 = "123a";
    char *data4 = "123";
    
    printf("%d\n",check(data1,3));
    printf("%d\n",check(data2,3));
    printf("%d\n",check(data3,3));
    printf("%d\n",check(data4,3));
    printf("%d\n",check(data4,4));
    return 0;
}