There are no conditional statements in the for statement in this code. Why?

u-- between two semicolons (;) is where you check the condition.

The conditional statement in C++ can accommodate any expression that can be valued, and most expressions in C++ return the value, so there is no error.

Because in terms of the conditional statement, whether it's an address value, a boolean value, or another value, if it's just 0, it's false, or it's true.

In this case, the conditional statement is u--, so if you want to change it to C#, just !Attach =

for (u = b.size(), v = b.back(); u-- != 0; v = p[v]) 
    b[u] = v;