String of sword finger offer question bank summary (II) (C language version)

The finger of the sword offer Question bank summary （ Two ） The string of （C Language version ）

topic 67： Convert a string to a number

• Specific requirements of the topic ：
• Put a number only or “+” or “-” The formed string is converted into the corresponding number .( Cannot use library functions atoi)
• Example ：
  • input: “123” output: 123
  • input: “+56” output:56
  • input：“-23” output：-23
• Use case testing ：
  • A functional test ： Consider that the input string represents a positive number 、 negative 、0.
  • Boundary value test ： There may be upper overflow or lower overflow （ That is, test the maximum or minimum integer ）
  • Special tests ： The input string is null The pointer , The input string is empty or non numeric string .
• Problem solving ：