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one。 String function 1. Find the strlen of the string length

Size_t strlen (const char * str)

The string ends with'\ 0', and the strlen function returns the number of characters that appear before'\ 0' in the string (excluding'\ 0').

The string pointed to by the parameter must end with'\ 0'.

Note that the return value of the function is size_t, which is unsigned.

Simulation and implementation of strlen

Size_t my_strlen (const char*str) {size_t count=0; while (* str) {str++; count++;} 2. Compare strcmp of string size

Int strcmp (const char * str1, const char * str2)

Compare from the location where str1 and str2 point, if you encounter two unequal characters or the\ 0 function ends and returns a value.

The character of the first string is larger than that of the second string and returns a number > 0.

The character of the first string is equal to the character of the second string that returns a number of = 0.

The character of the first string whose character is less than the second string returns the ptr2 return value > 0

Ptr1=ptr2 return value = 0

Ptr1

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