[英]C++ binary search struggle
Sorry for using polish names but I started with them and didin't want to confuse myself. 很抱歉使用波兰名字,但我从他们开始,并不想混淆自己。 I've got an assignment to find the possible answer to this equation
x^3 + px = q
, without negative numbers. 我有一个任务,找到这个方程的可能答案
x^3 + px = q
,没有负数。 Also I Have to use binary searching for that, it seemed to me pretty easy at first but I keep on getting wrong outputs. 此外,我必须使用二进制搜索,一开始我觉得很容易,但我继续得错输出。 Just wanted some advice on what I should focus on, not an entire solution.
只是想要一些关于我应该关注的建议,而不是整个解决方案。 Cheers!
干杯!
int main() {
int p, q, x;
cin >> p >> q;
int tablica[q-1];
for(int i = q-1; i>=0; i--){
tablica[i] = q;
q--;
}
bool znalezione = false;
int poczatek = 0;
int koniec = q-1;
while(!znalezione){
int srodek = (poczatek + koniec)/2;
tablica[srodek] = x;
if(x*x*x + p*x == q){
znalezione = true;
}
else
if(x*x*x + p*x > q){
koniec = srodek -1;
}
else
poczatek = srodek +1;
}
cout << x;
} }
You are trying to find the value of x
. 您正试图找到
x
的值。 The first thing that I notice is that x
is not initialized and then in the line tablica[srodek] = x
, you are assigning this to array, this will give a garbage value in tablica
. 我注意到的第一件事是
x
没有被初始化,然后在行tablica[srodek] = x
,你将它分配给数组,这将在tablica
给出一个垃圾值。
Additionally, you are never updating the value of x
. 此外,您永远不会更新
x
的值。 It will always display the value which was at the beginning (garbage value in your case) 它将始终显示开头的值(在您的情况下为垃圾值)
int tablica[q-1];
is not standard c++, use std::vector
. 不是标准的c ++,使用
std::vector
。 I'm not sure why you even need a table. 我不确定你为什么甚至需要一张桌子。 You've got the general idea but you never assigned anything to
x
. 你有一般的想法,但你从来没有给
x
分配任何东西。 Binary search algorithm is something like this: 二进制搜索算法是这样的:
std::optional<int> binary_search(int begin, int end, int element)
{
while(end-begin>0)
{
int midPoint = (end+begin)/2;
if(midPoint ==element)
return midPoint;
else if (midPoint > element)
begin = midPoint+1;
else
end = midPoint-1;
}
return {};
}
So all you have to do is replace insides of those if
statements with your equation. 因此,您所要做的就是用等式替换那些
if
语句的内部。
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