RT

例

while(left<=right){
         mid=(right+left)/2;
        if(check(mid)){
            high=mid;
            left=mid+1;
        }else{
            right=mid-1;
        }
    }

怎么确定while里面是left<=right 还是 left<right 还是left <right-1??

还有怎么确定left=mid+1还是left=mid？

QAQ