[经典算法] 排列组合-全排序

#include <gtest/gtest.h>
using namespace std;

// 全排列

void Swap(int* v1, int* v2)
{
    if (v1 == v2)
        return;

    int value = *v1;
    *v1 = *v2;
    *v2 = value;
}

void ShowResult(int data[], int size, int count)
{
    for (int i = 0; i < size; ++i)
    {
        cout << data[i] << " ";
    }

    if (count % 8 == 0)
    {
        cout << endl;
    }
    else
    {
        cout << "  ";
    }
}

void Permutation(int data[], int begin, int end, int& count)
{    
    if (begin < end)
    {
        for (int i = begin; i < end; ++i)
        {
            Swap(&data[begin], &data[i]);
            Permutation(data, begin+1, end, count);
            Swap(&data[begin], &data[i]);
        }
    }
    else
    {
        ++count;
        ShowResult(data, end ,count);
    }
}

TEST(Algo, tPermutation)
{
    int data[] = {1,2,3,4};
    int nCount = 0;

    // 4个数 4! = 24
    Permutation(data, 0, 4, nCount);
    ASSERT_EQ(nCount, 24);

    // 5个数 5! = 120
    int data1[] = {1,2,3,4,5};
    nCount = 0;
    Permutation(data1, 0, 5, nCount);
    ASSERT_EQ(nCount, 120);

    // 6个数 6! = 720
    int data2[] = {1,2,3,4,5,6};
    nCount = 0;
    Permutation(data2, 0, 6, nCount);
    ASSERT_EQ(nCount, 720);
}