pid=5105" target="_blank" style="">题目链接:hdu 5105 Math Problem 题目大意:给定a.b,c,d.l,r.表示有一个函数f(x)=|a∗x3+b∗x2+c∗x+d|(L≤x≤R),求函数最大值. 解题思路:考虑极点就可以,将函数求导后得到f′(x)=0的x,即为极值点.在极值点处函数的单调性会发生变化,所以最大值一定就在区间边界和极值点上.注意a=0.b=0的情况,以及极值点不在区间上. #in…

官方题解: f(x)=|a∗x3+b∗x2+c∗x+d|, 求最大值.令g(x)=a∗x3+b∗x2+c∗x+d,f(x)的最大值即为g(x)的正最大值,或者是负最小值.a!=0时, g′(x)=3∗a∗x2+2∗b∗x+c 求出g′(x)的根(若存在,x1,x2,由导数的性质知零点处有极值.ans=max(f(xi)|L≤xi≤R).然后考虑两个端点的特殊性有ans=max(ans,f(L),f(R)). 当时 x = -c/(2*b) 写成 x = -c/2*b 了,然后过pretest了.…

让求  f(x)=|a∗x3+b∗x2+c∗x+d|(L≤x≤R)的最大值 这个题目讨论a和b的值,如果a==0的话,那么这个方程就变成了一个一元二次方程,直接找端点和对称轴(如果对称轴在给定的区间内)处的函数值就行,如果a != 0,那么求导,求导之后判断二次方程的delta,如果delta小于等于0,说明是单调的,那么最值还是端点处取到,如果delta大于0, 那么就要比较两个极点(如果极点在给定的区间内)处的值和端点值的大小就行了. /***************************…

You are given a positive integer n, please count how many positive integers k satisfy kk≤nkk≤n.  InputThere are no more than 50 test cases. Each case only contains a positivse integer n in a line. 1≤n≤10^18OutputFor each test case, output an integer…

题目链接 大意:给你两个数X,YX,YX,Y,让你找两个数a,ba,ba,b,满足a+b=X,lcm(a,b)=Ya+b=X,lcm(a,b)=Ya+b=X,lcm(a,b)=Y. 思路:枚举gcd(a,b)gcd(a,b)gcd(a,b),假设gcd(a,b)=k,那么a=xa∗k,b=xb∗k,gcd(a,b)=k,那么a=x_a*k,b=x_b*k,gcd(a,b)=k,那么a=xa​∗k,b=xb​∗k,化简上面给的两个式子即可得到 xa+xb=Xk,xa∗xb=Ykx_a+x_b=\f…

Hard problem 题目链接: http://acm.split.hdu.edu.cn/showproblem.php?pid=5858 Description cjj is fun with math problem. One day he found a Olympic Mathematics problem for primary school students. It is too difficult for cjj. Can you solve it? Give you the…

主题链接:http://acm.hdu.edu.cn/showproblem.php?pid=5055 Problem Description Recently, Bob has been thinking about a math problem. There are N Digits, each digit is between 0 and 9. You need to use this N Digits to constitute an Integer. This Integer need…

题目链接:HDU - 5170GTY's math problem 题目描述 Description GTY is a GodBull who will get an Au in NOI . To have more time to learn algorithm knowledge, he never does his math homework. His math teacher is very unhappy for that, but she can't do anything beca…

任意门:http://acm.hdu.edu.cn/showproblem.php?pid=1757 A Simple Math Problem Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 6621    Accepted Submission(s): 4071 Problem Description Lele now is thin…

A Simple Math Problem Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)Total Submission(s): 2441    Accepted Submission(s): 1415 Problem Description Lele now is thinking about a simple function f(x). If x < 10 f(x) =…