Is legal in the middle of the binary binary answer why don't we talk about the title of the mid value will change, sometimes is mid=(L + R)/2, is sometimes mid=(L + R + 1)/2;
What good method can be well understood this boundary? Or is there a better template
I use the template is like this:
Max:

 void of solve () {
Int l=0, r=MAXN; 
for(int i=0; i<100; I++) {
Int mid=(r + l + 1)/2;//this place what determine 
If (check (mid)) {
L=mid; 
} else {
R=mid - 1; 
} 
} 
Cout} 

A minimum value:

 void of solve () {
Int lb=0, rb=maxn; 
for(int i=0; i<100; I++) {
Int mid=(lb + rb + 1)/2;//this place what determine 
If (check (mid)) {
Rb=mid; 
} else {
Lb=mid + 1; 
} 
} 
Cout}