IP string to integer [interview]

I went to the O & M department of an Internet company for an interview. Although I wrote a question in five minutes, there were many mistakes. Fortunately, I only pointed out one or two questions. Let alone run it! Recently, I was preparing to apply for a job. I used it last night for practice. I didn't pick it up for more than two hours. I went to bed more than 12 o'clock in the evening and got up and changed it, but it was still not completely correct. After breakfast today, I debugged it for another hour and finally succeeded! Share it!

First, sum up experience: 1. You must think carefully before writing, which is more time-saving than writing and modifying!

2. If the basic confirmation is a syntax error, you can adjust it slowly. If your logic is unclear, simply repeat it! Have the courage to refactor!

1 # include <stdio. h> 2 // The program function converts IP addresses such as "192.168.1.29" to an integer of 3 int main () (equivalent to the one after the decimal point is removed () {4 5 char ip [] = "0.3.2.1. "; // if your machine sizeof (int) is 2 bytes, consider overflow! 6 7 int sum = 0, I = 0, j = 0, n = 0; // erroor1: I is not initialized. A segment error occurs when the subscript is out of bounds! 8 int cnt = 4; 9 char tmp [4]; 10 11 while (cnt> 0) {12 int tmpsum = 0; // do not remember the start sum initialization, initialization is required for any new variable while writing; otherwise, the result is incorrect! 13 14 if (ip [j]! = '. ') {15 tmp [I] = ip [j]; 16 // printf ("% c \ n", ip [j]); 17 I ++; j ++; 18} else {19 I = 0; j ++; 20 tmpsum = atoi (tmp); 21 // printf ("* % d \ n ", tmpsum); 22 if (cnt! = 1) {23 for (n = cnt-1; n> = 1; n --) 24 tmpsum * = 256; 25 printf ("** % d \ n", tmpsum ); 26} 27 cnt --; 28} 29 30 sum + = tmpsum; 31 // printf ("*** % d \ n", tmpsum ); // 32} 33 printf ("% d \ n", sum); 34 return 0; 35}

 

I also learned how to debug the gdb program today. I was too lazy to debug the program without IDE. Today I see Chen Hao's articles in the "debug program with GDB" series, which I would like to recommend to you!