Note offer prove safety questions surface 12 is in the path matrix ----

Title: Please design a function that determines whether there is a route that contains all the characters of a character string in a matrix. The path can start from any of a matrix of cells, each step in the matrix can be left, right, up and down movement of a grid. If one path after a grid matrix, then the path can not enter the grid again. For example, a character string containing "bfce" in the following path in the 3x4 matrix (the path indicated by an underline letters). However, the matrix does not contain the path string "abfb" because a character string b occupy the first row of the first matrix after the second grid, the grid can not enter the path again.

a	b	t	g
c	f	c	s
j	d	e	h

Test Case:

• Functional test (presence or absence of a path in a matrix of rows and columns).
• Boundary value test (only one row in the matrix or only one; matrices and all the letters are the same path).
• Special test input (input nullptr pointer).

Test code:

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);
}

This question test sites:

• Examine the candidate's understanding of backtracking. Usually find the path on the two-dimensional matrix of these problems can be solved apply backtracking.
• Examine the candidates ability to program the array. We generally regarded as a two-dimensional matrix array. Only fully understand the characteristics of the array, will it be possible to quickly code backtracking is properly implemented.

Implementation code:

#include <cstdio>
#include <cstring>
#include <stack>

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)
        return false;
    bool *visited = new bool[rows * cols];
    memset(visited, 0, rows * cols);

    int pathLength = 0;
    for(int row = 0; row < rows; ++row)
    {
        for(int col = 0; col < cols; ++col)
        {
            if(hasPathCore(matrix, rows, cols, row, col, str,
                pathLength, 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')
        return true;
    bool hasPath = false;
    if(row >= 0 && row < rows && col >= 0 && col < cols
        && matrix[row * cols + col] == str[pathLength]
        && !visited[row * cols + col])
    {
        ++pathLength;
        visited[row * cols + col] = true;
        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);
        if(!hasPath)
        {
            --pathLength;
            visited[row * cols + col] = false;
        }
    }
    return hasPath;
}
int main(int argc, char* argv[])
{
    Test1();
    Test2();
    Test3();
    Test4();
    Test5();
    Test6();
    Test7();
    Test8();
    Test9();
    Test10();
    Test11();
    Test12();
    return 0;
}