矩阵中的路径

解答：

public class Solution {

    public static boolean hasPath(char[] matrix, int rows, int cols, char[] str) {
        if(matrix.length <= 0 || rows < 0 || cols < 0 || str.length <= 0) {
            return false;
        }
        
        boolean visited[] = new boolean[rows * cols];
        int [] index = {0};
        for(int i = 0;i < rows;i ++) {
            for(int j = 0;j < cols;j ++) {
                if(isPath(matrix, rows, cols, i, j, str, visited, index)) {
                    return true;
                }
            }
        }
        return false;
    }
    
    public static boolean isPath(char[] matrix, int rows, int cols, int row, int col, char[] str, boolean visited[], int [] index) {
        if(index[0] == str.length) {
            return true;
        }
        
        boolean flag = false; 
        //当前点折算到原数组的位置是：row * cols + col
        if(row >= 0 && row < rows && col >= 0 && col < cols 
           && !visited[row * cols + col] && matrix[row * cols + col] == str[index[0]]) {
            index[0] ++;    //指针右移
            visited[row * cols + col] = true;
            
            //第一个点是合法的起点之后开始回溯:上下左右进行搜索
            flag = isPath(matrix, rows, cols, row - 1, col, str, visited, index) || 
                   isPath(matrix, rows, cols, row + 1, col, str, visited, index) ||
                   isPath(matrix, rows, cols, row, col - 1, str, visited, index) ||
                   isPath(matrix, rows, cols, row, col + 1, str, visited, index);

            if(!flag) {     //恢复现场
                index[0] --;
                visited[row * cols + col] = false;
            }
        }
        
        return flag;
    }
    
    public static void main(String[] args) {
        String str = "ABCEHJIGSFCSLOPQADEEMNOEADIDEJFMVCEIFGGS";
        char[] matrix = str.toCharArray();
        String str2 = "SGGFIECVAASABCEEJIGOEM";
        char[] c = str2.toCharArray();
        System.out.println(hasPath(matrix, 5, 8, c));
    }

}