c,loops,while-loop , while(*s++=*t++) is equivalent to which expression?

while(*s++=*t++) is equivalent to which expression?


Tag: c,loops,while-loop

A. while (*t) *s++ = *t++;
B. do { *s = *t++; } while (*s++);
C. while (*s) *s++ = *t++;
D. do { *s++ = *t++; } while (*t);

The answer is B, why others are wrong?


A.) vs. B.)

B will always copy the first value before checking if the result is 0.
A will do the test first, and if the result is 0, it will stop before ever copying the first value.

C.) vs. B.)

Similar to A, C does the test first, and will never copy a value if the first value is 0.

D.) vs. B.) After copying a value, T is incremented, then the test is done against T (the next value), instead of the previous T.


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