// 面試題：矩陣中的路徑
// 題目：請設計一個函數，用來判斷在一個矩陣中是否存在一條包含某字符串所有
// 字符的路徑。路徑可以從矩陣中任意一格開始，每一步可以在矩陣中向左、右、
// 上、下移動一格。如果一條路徑經過了矩陣的某一格，那麽該路徑不能再次進入
// 該格子。例如在下面的3×4的矩陣中包含一條字符串“bfce”的路徑（路徑中的字
// 母用下劃線標出）。但矩陣中不包含字符串“abfb”的路徑，因為字符串的第一個
// 字符b占據了矩陣中的第一行第二個格子之後，路徑不能再次進入這個格子。
// A B T G
// C F C S
// J D E H
 



#include <string>

using namespace std;

bool hasPathCore(const char* matrix, int rows, int cols, int row, int col, const char* str, int& pathLength, bool* visited);

bool hasPath(const char* matrix, int rows, int cols, const char* str)
{
    if (matrix == nullptr || rows < 1
 
 || cols < 1 || str == nullptr)//負面測試
        return false;

    bool *visited = new bool[rows * cols];//用來檢測某個節點是否已經走過了
    memset(visited, 0, rows * cols);//將開辟出來的visitedp[rows * cols]裏都設為0

    int pathLength = 0;//待檢測字符長度變量
    for (int row = 0; row < rows; ++row)
    {
        for (int col = 0
 
; col < cols; ++col)
        {
            if (hasPathCore(matrix, rows, cols, row, col, str, pathLength, visited))//遍歷每個點，作為起點，開始檢測
            {
                delete[] visited;
                return true;
            }
        }
    }

    delete[] visited;

    return false;
}

bool hasPathCore(const char* matrix, int rows, int cols, int row,
    int col, const char* str, int& pathLength, bool* visited)
{
    if (str[pathLength] == ‘\0‘)//遞歸停止條件一，我經找到最後一個字符了，查找完畢，返回正確
        return true;

    bool hasPath = false;
    if (row >= 0 && row < rows && col >= 0 && col < cols
        && matrix[row * cols + col] == str[pathLength]
        && !visited[row * cols + col])//這個是我沒有走過的節點中，那符合我現在查找的字符A嗎
    {
        ++pathLength;//符合，那找下個字符B
        visited[row * cols + col] = true;//這個點在這個起點的時候，我走過了

        hasPath = hasPathCore(matrix, rows, cols, row, col - 1,
            str, pathLength, visited)
            || hasPathCore(matrix, rows, cols, row - 1, col,
                str, pathLength, visited)
            || hasPathCore(matrix, rows, cols, row, col + 1,
                str, pathLength, visited)
            || hasPathCore(matrix, rows, cols, row + 1, col,
                str, pathLength, visited);//以上下左右節點分別為起點檢測字符B

        if (!hasPath)//完了走不通
        {
            --pathLength;//這個節點A以後的沒希望了，那我退回一下，繼續找A
            visited[row * cols + col] = false;//那當我這個點沒走過吧
        }
    }

    return hasPath;
}

// ====================測試代碼====================
void Test(const char* testName, const char* matrix, int rows, int cols, const char* str, bool expected)
{
    if (testName != nullptr)
        printf("%s begins: ", testName);

    if (hasPath(matrix, rows, cols, str) == expected)
        printf("Passed.\n");
    else
        printf("FAILED.\n");
}

//ABTG
//CFCS
//JDEH

//BFCE
void Test1()
{
    const char* matrix = "ABTGCFCSJDEH";
    const char* str = "BFCE";

    Test("Test1", (const char*)matrix, 3, 4, str, true);
}

//ABCE
//SFCS
//ADEE

//SEE
void Test2()
{
    const char* matrix = "ABCESFCSADEE";
    const char* str = "SEE";

    Test("Test2", (const char*)matrix, 3, 4, str, true);
}

//ABTG
//CFCS
//JDEH

//ABFB
void Test3()
{
    const char* matrix = "ABTGCFCSJDEH";
    const char* str = "ABFB";

    Test("Test3", (const char*)matrix, 3, 4, str, false);
}

//ABCEHJIG
//SFCSLOPQ
//ADEEMNOE
//ADIDEJFM
//VCEIFGGS

//SLHECCEIDEJFGGFIE
void Test4()
{
    const char* matrix = "ABCEHJIGSFCSLOPQADEEMNOEADIDEJFMVCEIFGGS";
    const char* str = "SLHECCEIDEJFGGFIE";

    Test("Test4", (const char*)matrix, 5, 8, str, true);
}

//ABCEHJIG
//SFCSLOPQ
//ADEEMNOE
//ADIDEJFM
//VCEIFGGS

//SGGFIECVAASABCEHJIGQEM
void Test5()
{
    const char* matrix = "ABCEHJIGSFCSLOPQADEEMNOEADIDEJFMVCEIFGGS";
    const char* str = "SGGFIECVAASABCEHJIGQEM";

    Test("Test5", (const char*)matrix, 5, 8, str, true);
}

//ABCEHJIG
//SFCSLOPQ
//ADEEMNOE
//ADIDEJFM
//VCEIFGGS

//SGGFIECVAASABCEEJIGOEM
void Test6()
{
    const char* matrix = "ABCEHJIGSFCSLOPQADEEMNOEADIDEJFMVCEIFGGS";
    const char* str = "SGGFIECVAASABCEEJIGOEM";

    Test("Test6", (const char*)matrix, 5, 8, str, false);
}

//ABCEHJIG
//SFCSLOPQ
//ADEEMNOE
//ADIDEJFM
//VCEIFGGS

//SGGFIECVAASABCEHJIGQEMS
void Test7()
{
    const char* matrix = "ABCEHJIGSFCSLOPQADEEMNOEADIDEJFMVCEIFGGS";
    const char* str = "SGGFIECVAASABCEHJIGQEMS";

    Test("Test7", (const char*)matrix, 5, 8, str, false);
}

//AAAA
//AAAA
//AAAA

//AAAAAAAAAAAA
void Test8()
{
    const char* matrix = "AAAAAAAAAAAA";
    const char* str = "AAAAAAAAAAAA";

    Test("Test8", (const char*)matrix, 3, 4, str, true);
}

//AAAA
//AAAA
//AAAA

//AAAAAAAAAAAAA
void Test9()
{
    const char* matrix = "AAAAAAAAAAAA";
    const char* str = "AAAAAAAAAAAAA";

    Test("Test9", (const char*)matrix, 3, 4, str, false);
}

//A

//A
void Test10()
{
    const char* matrix = "A";
    const char* str = "A";

    Test("Test10", (const char*)matrix, 1, 1, str, true);
}

//A

//B
void Test11()
{
    const char* matrix = "A";
    const char* str = "B";

    Test("Test11", (const char*)matrix, 1, 1, str, false);
}

void Test12()
{
    Test("Test12", nullptr, 0, 0, nullptr, false);
}

int main(int argc, char* argv[])
{
    Test1();
    Test2();
    Test3();
    Test4();
    Test5();
    Test6();
    Test7();
    Test8();
    Test9();
    Test10();
    Test11();
    Test12();
    system("pause");
    return 0;
}

《劍指offer》第九_一題（矩陣中的路徑）