367. 有效的完全平方数C

bool isPerfectSquare(int num) {
    if(num==1) return true;
    if(num==2) return false;
    long head=2,tail=num-1;
    while(head<=tail){
        long mid=(head+tail)/2;
        long t =mid*mid;
        if(t<(long)num){
            head=mid+1;
        }else if(t >(long)num){
            tail=mid-1;
        }else{
            return true;
        }
    }
    return false;
}

结果：