Z形打印

package 每日算法学习打卡.算法打卡.七月份.七月二十七号;

public class test1 {
    public static void main(String[] args) {
        int[][] matrix = {
                {1, 2, 3, 4},
                {5, 6, 7, 8},
                {9, 10, 11, 12},
        };
        print(matrix);
    }

    static void print(int[][] matrix) {
        int r = 0, m = matrix.length;
        int l = 0, n = matrix[0].length;
        boolean l2r = true;
        while (r < m && l < n) {
            if (l2r) {
                System.out.println(matrix[r][l] + " ");
                //如果在走上坡路
                if (r == 0 && l < n - 1) {
                    l2r = !l2r;
                    l++;
                    continue;
                    //如果已经走到末尾了，行号就进行减一操作
                } else if (r > 0 && l == n - 1) {
                    l2r = !l2r;
                    r++;
                    continue;
                    //其余的情况都是在走上坡路
                } else {
                    r--;
                    l++;
                }
            } else {
                //如果是在走下坡路
                System.out.println(matrix[r][l] + " ");
                //如果走到左边界的时候，就向下走一格
                if(l == 0 && r <m-1){
                    l2r = !l2r;
                    r++;
                    continue;
                }else if( r == m-1){
                    l2r = !l2r;
                    l++;
                    continue;
                }else{
                    r++;
                    l--;
                }
            }
        }
    }
}

边界为1的最大子方阵

package 每日算法学习打卡.算法打卡.七月份.七月二十七号;



    public class test2 {
        public static int solve(int[][] matrix, int N) {
            int n = N; // 阶数
            boolean flag = false;
            while (n > 0) {
                for (int i = 0; i < N; i++, flag = false) {
                    if (i + n > N)
                        break;
                    for (int j = 0; j < N; j++, flag = false) {
                        if (j + n > N)
                            break;
                        // 当前节点开始查看是否满足均为1
                        int r = i, c = j;
                        while (c < j + n) { // 往右走
                            if (matrix[r][c] == 0) {
                                flag = true;
                                break;
                            }
                            c++;
                        }
                        if (flag) {
                            continue;
                        }
                        c--; // 复原
                        while (r < i + n) { // 往下走
                            if (matrix[r][c] == 0) {
                                flag = true;
                                break;
                            }
                            r++;
                        }
                        if (flag) {
                            continue;
                        }
                        r--;
                        while (c >= j) { // 往左走
                            if (matrix[r][c] == 0) {
                                flag = true;
                                break;
                            }
                            c--;
                        }
                        if (flag) {
                            continue;
                        }
                        c++;
                        while (r >= i) { // 往上走
                            if (matrix[r][c] == 0) {
                                flag = true;
                                break;
                            }
                            r--;
                        }
                        if (flag) {
                            continue;
                        }
                        r++;
                        return n;
                    }
                }
                n--;
            }
            return n; // 全是0，直接返回
        }

        public static void main(String[] args) {
            int[][] matrix = {
                    {0, 1, 1, 1, 1},
                    {0, 1, 0, 0, 1},
                    {0, 1, 0, 0, 1},
                    {0, 1, 1, 1, 1},
                    {0, 1, 0, 1, 1}
            };
            int res = solve(matrix, 5);
            System.out.println("result: " + res);
        }
    }