Question

我已经被困在这个问题上差不多一个星期了，我想我需要一些帮助来解决它。我以这种格式给出了一组比较：

第一行表示有5个元素可以比较（1-5）
第二行表示将有多少比较声明从第三行开始是比较语句。第一个元素优于第二个元素。因此，在这种情况下，1> 2，和2> 3和3> 4等等。

我应该输出比每个元素更好和更差的元素数量。所以没有数字比元素1更好，并且有3个数字比1（2,3,4）差。我想你应该已经明白了。输出应为：

1: better: 0 worse: 3
2: better: 1 worse: 2
3: better: 2 worse: 1
4: better: 5 worse: 0
5: better: 1 worse: 1
6: better: 0 worse: 2

到目前为止，这是我的实现

class Student{
public:
vector<int> better;
vector<int> worse;
};

void addComp(Student* student, int a, int b){

//push all worse elements into their better elements (there will be    duplicate)
student[a].worse.push_back(b);
vector<int>::iterator bIter = student[b].worse.begin();
vector<int>::iterator aIter = student[a].better.begin();

while (aIter != student[a].better.end())
{
    student[*aIter].worse.push_back(b);
    aIter++;
}

while (bIter != student[b].worse.end())
{
    student[a].worse.push_back(*bIter);

    aIter = student[a].better.begin();
    while (aIter != student[a].better.end())
    {
        student[*aIter].worse.push_back(*bIter);
        aIter++;
    }
    bIter++;
}

//push all better elements into their worse elements (there will be duplicate)
student[b].better.push_back(a);
bIter = student[b].worse.begin();
aIter = student[a].better.begin();

while (bIter != student[b].worse.end())
{
    student[*bIter].better.push_back(a);
    bIter++;
}

while (aIter != student[a].better.end())
{
    student[b].better.push_back(*aIter);

    bIter = student[b].worse.begin();
    while (bIter != student[b].worse.end())
    {
        student[*bIter].better.push_back(*aIter);
        bIter++;
    }
    aIter++;
 }
}

int main()
{
int studentCount, inputCount, testCase;
int a, b;
Student* student;

cin >> testCase;
while (testCase > 0)
{
    //The number of student that will be compared
    cin >> studentCount;

    student = new Student[studentCount + 1];

    //The number of comparison input
    cin >> inputCount;

    while (inputCount > 0)
    {
        cin >> a >> b;
        addComp(student, a, b);
        inputCount--;
    }

    //Start counting the number of better and worse student for each student
    for (int i = 1; i <= studentCount; i++)
    {
        //Remove duplicate from worse array
        sort(student[i].worse.begin(), student[i].worse.end());
        vector<int>::iterator last = std::unique(student[i].worse.begin(), student[i].worse.end());
        student[i].worse.erase(last, student[i].worse.end());

        //Remove duplicate from better array
        sort(student[i].better.begin(), student[i].better.end());
        vector<int>::iterator last2 = std::unique(student[i].better.begin(), student[i].better.end());
        student[i].better.erase(last2, student[i].better.end());

        cout << i " better: " << student[i].better.size() << " worse: " << student[i].worse.size() << endl;
    }
    delete [] student;
    testCase--;
 }
}

它工作正常，但是对于这个问题来说效率不高。要比较的元素数量最多可达50，比较语句的数量最多可达10000s比较语句。这仅适用于一个测试用例。可以有多个测试用例。如果您能指出我更有效的算法或帮助优化我的代码，我将非常感激。

Answer 1

如何尝试消除addComp中的重复元素？此外，您可以在addComp。

的同时对它们进行排序

我建议你使用set而不是vector，因为set可以是唯一的。步骤1.用集合替换向量第2步。用insert替换push_back 步骤3.删除排序部分

#include <set>
#include <algorithm>
#include <iostream>
using namespace std;

class Student{
public:
set<int> better;
set<int> worse;
};

void addComp(Student* student, int a, int b){

//push all worse elements into their better elements (there will be    duplicate)
student[a].worse.insert(b);
set<int>::iterator bIter = student[b].worse.begin();
set<int>::iterator aIter = student[a].better.begin();

while (aIter != student[a].better.end())
{
    student[*aIter].worse.insert(b);
    aIter++;
}

while (bIter != student[b].worse.end())
{
    student[a].worse.insert(*bIter);

    aIter = student[a].better.begin();
    while (aIter != student[a].better.end())
    {
        student[*aIter].worse.insert(*bIter);
        aIter++;
    }
    bIter++;
}

//push all better elements into their worse elements (there will be duplicate)
student[b].better.insert(a);
bIter = student[b].worse.begin();
aIter = student[a].better.begin();

while (bIter != student[b].worse.end())
{
    student[*bIter].better.insert(a);
    bIter++;
}

while (aIter != student[a].better.end())
{
    student[b].better.insert(*aIter);

    bIter = student[b].worse.begin();
    while (bIter != student[b].worse.end())
    {
        student[*bIter].better.insert(*aIter);
        bIter++;
    }
    aIter++;
 }
}

int main()
{
int studentCount, inputCount, testCase;
int a, b;
Student* student;

cin >> testCase;
while (testCase > 0)
{
    //The number of student that will be compared
    cin >> studentCount;

    student = new Student[studentCount + 1];

    //The number of comparison input
    cin >> inputCount;

    while (inputCount > 0)
    {
        cin >> a >> b;
        addComp(student, a, b);
        inputCount--;
    }

    //Start counting the number of better and worse student for each student
    for (int i = 1; i <= studentCount; i++)
    {
        cout << i << " better: " << student[i].better.size() << " worse: " << student[i].worse.size() << endl;
    }
    delete [] student;
    testCase--;
 }
}

传递性比较的优化（A> B，B> C => A> C）

1 个答案: