《劍指offer》第五十九題（滑動視窗的最大值）

// 面試題59（一）：滑動視窗的最大值

// 題目：給定一個數組和滑動視窗的大小，請找出所有滑動窗口裡的最大值。例如，

// 如果輸入陣列{2, 3, 4, 2, 6, 2, 5, 1}及滑動視窗的大小3，那麼一共存在6個

// 滑動視窗，它們的最大值分別為{4, 4, 6, 6, 6, 5}，

#include <iostream>

#include <vector>

#include <deque>

using namespace std;

vector<int> maxInWindows(const vector<int>& num, unsigned int size)

{

    vector<int> maxInWindows;

    if (num.size() >= size && size >= )

    {

        deque<int> index;

        for (unsigned int i = ; i < size; ++i)//先找出第一個滑窗裡的最大值的座標，放入佇列頭

        {

            while (!index.empty() && num[i] >= num[index.back()])

                index.pop_back();

            index.push_back(i);

        }

        for (unsigned int i = size; i < num.size(); ++i)//對之後的每個點

        {

            maxInWindows.push_back(num[index.front()]);//先把佇列頭放入maxInWindows

            while (!index.empty() && num[i] >= num[index.back()])//如果佇列不為空且當前點大於尾節點，就刪除尾節點，直到尾節點不小於當前節點

                index.pop_back();

            if (!index.empty() && index.front() <= (int)(i - size))//如果佇列不為空，且頭結點的位置小於當前位置減去滑窗長度，說明這個最大值不再滑窗內了，刪除

                index.pop_front();

            index.push_back(i);//插入當前點的座標

        }

        maxInWindows.push_back(num[index.front()]);//最後那個值沒在迴圈中插入maxInWindows，要額外寫一句

    }

    return maxInWindows;

}

// ====================測試程式碼====================

void Test(const char* testName, const vector<int>& num, unsigned int size, const vector<int>& expected)

{

    if (testName != nullptr)

        printf("%s begins: ", testName);

    vector<int> result = maxInWindows(num, size);

    vector<int>::const_iterator iterResult = result.begin();

    vector<int>::const_iterator iterExpected = expected.begin();

    while (iterResult < result.end() && iterExpected < expected.end())

    {

        if (*iterResult != *iterExpected)

            break;

        ++iterResult;

        ++iterExpected;

    }

    if (iterResult == result.end() && iterExpected == expected.end())

        printf("Passed.\n");

    else

        printf("FAILED.\n");

}

void Test1()

{

    int num[] = { , , , , , , ,  };

    vector<int> vecNumbers(num, num + sizeof(num) / sizeof(int));

    int expected[] = { , , , , ,  };

    vector<int> vecExpected(expected, expected + sizeof(expected) / sizeof(int));

    unsigned int size = ;

    Test("Test1", vecNumbers, size, vecExpected);

}

void Test2()

{

    int num[] = { , , -, -, , , ,  };

    vector<int> vecNumbers(num, num + sizeof(num) / sizeof(int));

    int expected[] = { , , , , ,  };

    vector<int> vecExpected(expected, expected + sizeof(expected) / sizeof(int));

    unsigned int size = ;

    Test("Test2", vecNumbers, size, vecExpected);

}

// 輸入陣列單調遞增

void Test3()

{

    int num[] = { , , , , , , ,  };

    vector<int> vecNumbers(num, num + sizeof(num) / sizeof(int));

    int expected[] = { , , , ,  };

    vector<int> vecExpected(expected, expected + sizeof(expected) / sizeof(int));

    unsigned int size = ;

    Test("Test3", vecNumbers, size, vecExpected);

}

// 輸入陣列單調遞減

void Test4()

{

    int num[] = { , , , , , ,  };

    vector<int> vecNumbers(num, num + sizeof(num) / sizeof(int));

    int expected[] = { , ,  };

    vector<int> vecExpected(expected, expected + sizeof(expected) / sizeof(int));

    unsigned int size = ;

    Test("Test4", vecNumbers, size, vecExpected);

}

// 滑動視窗的大小為1

void Test5()

{

    int num[] = { , , ,  };

    vector<int> vecNumbers(num, num + sizeof(num) / sizeof(int));

    int expected[] = { , , ,  };

    vector<int> vecExpected(expected, expected + sizeof(expected) / sizeof(int));

    unsigned int size = ;

    Test("Test5", vecNumbers, size, vecExpected);

}

// 滑動視窗的大小等於陣列的長度

void Test6()

{

    int num[] = { , , ,  };

    vector<int> vecNumbers(num, num + sizeof(num) / sizeof(int));

    int expected[] = {  };

    vector<int> vecExpected(expected, expected + sizeof(expected) / sizeof(int));

    unsigned int size = ;

    Test("Test6", vecNumbers, size, vecExpected);

}

// 滑動視窗的大小為0

void Test7()

{

    int num[] = { , , ,  };

    vector<int> vecNumbers(num, num + sizeof(num) / sizeof(int));

    vector<int> vecExpected;

    unsigned int size = ;

    Test("Test7", vecNumbers, size, vecExpected);

}

// 滑動視窗的大小大於輸入陣列的長度

void Test8()

{

    int num[] = { , , ,  };

    vector<int> vecNumbers(num, num + sizeof(num) / sizeof(int));

    vector<int> vecExpected;

    unsigned int size = ;

    Test("Test8", vecNumbers, size, vecExpected);

}

// 輸入陣列為空

void Test9()

{

    vector<int> vecNumbers;

    vector<int> vecExpected;

    unsigned int size = ;

    Test("Test9", vecNumbers, size, vecExpected);

}

int main(int argc, char* argv[])

{

    Test1();

    Test2();

    Test3();

    Test4();

    Test5();

    Test6();

    Test7();

    Test8();

    Test9();

    system("pause");

    return ;

}