剑指offer65：矩阵中的路径（二维数组，二分查找）

 1 class Solution {
 2 public:
 3     bool hasPathCore(const char *matrix, int rows, int cols, int row, int col, const char *str, int &pathLen, bool *visited)
 4     {
 5         //一定注意开头两个判定的顺序，如果str已经全部监测了，那么就直接返回true，不需要进行下一步检测
 6         if (str[pathLen] == ‘\0‘)return true;
 7 
 8         //需要进一步检测才检查状态对不对
 9         if ((row < 0) || (col < 0) || (row >= rows) || (col >= cols) || (visited[row*cols + col]))return false;
10 
11         bool resu = false;
12         //检查当前字符是否满足
13         if (matrix[row*cols + col] == str[pathLen]){
14             pathLen++;
15             visited[row*cols + col] = true;
16 
17             resu = hasPathCore(matrix, rows, cols, row + 1, col, str, pathLen, visited) ||
18                    hasPathCore(matrix, rows, cols, row - 1, col, str, pathLen, visited) ||
19                    hasPathCore(matrix, rows, cols, row, col - 1, str, pathLen, visited) ||
20                    hasPathCore(matrix, rows, cols, row, col + 1, str, pathLen, visited);
21 
22             //如果resu为假，当前格子不可能处在路径的第pathLen个位置上（所有可能性都检查了）
23             if (!resu){
24                 pathLen--;                          //从当前分支退出，把pathLength减回去，visited清空
25                 visited[row*cols + col] = false;
26             }
27         }
28         return resu;
29     }
30     
31     bool hasPath(char* matrix, int rows, int cols, char* str)
32     {
33         if ((matrix == NULL) || (rows <= 0) || (cols <= 0) || (str == NULL)){
34             return false;
35         }
36 
37         bool *visited = (bool *)malloc(rows*cols);
38        //bool *visited = new bool[rows * cols]; //记录当前路径已访问的节点
39         memset(visited, false, rows*cols);
40 
41         bool resu;
42         int pathLen = 0;
43         //遍历所有可能的入口，发现第一条路径时就结束
44         for (int i = 0; i != rows; i++){
45             for (int j = 0; j != cols; j++){
46                 if (hasPathCore(matrix, rows, cols, i, j, str, pathLen, visited)){
47                     free(visited);
48                     return true;
49                 }
50             }
51         }
52         free(visited);
53         return false;
54     }
55 };