习题1 给定一个正方形矩阵matrix，原地调整成顺时针90度转动的样子

a b c g d a
d e f h e b
g h i i f c

public static void spiralOrderPrint(int[][] matrix) {
		int tR = 0;
		int tC = 0;
		int dR = matrix.length - 1;
		int dC = matrix[0].length - 1;
		while (tR <= dR && tC <= dC) {
			printEdge(matrix, tR++, tC++, dR--, dC--);
		}
	}

	public static void printEdge(int[][] m, int tR, int tC, int dR, int dC) {
		if (tR == dR) {
			for (int i = tC; i <= dC; i++) {
				System.out.print(m[tR][i] + " ");
			}
		} else if (tC == dC) {
			for (int i = tR; i <= dR; i++) {
				System.out.print(m[i][tC] + " ");
			}
		} else {
			int curC = tC;
			int curR = tR;
			while (curC != dC) {
				System.out.print(m[tR][curC] + " ");
				curC++;
			}
			while (curR != dR) {
				System.out.print(m[curR][dC] + " ");
				curR++;
			}
			while (curC != tC) {
				System.out.print(m[dR][curC] + " ");
				curC--;
			}
			while (curR != tR) {
				System.out.print(m[curR][tC] + " ");
				curR--;
			}
		}
	}

	public static void main(String[] args) {
		int[][] matrix = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 },
				{ 13, 14, 15, 16 } };
		spiralOrderPrint(matrix);

	}

习题2 给定一个长方形矩阵matrix，实现转圈打印

a b c d
e f g h
i j k L
打印顺序：a b c d h L k j I e f g

public static void rotate(int[][] matrix) {
		int a = 0;
		int b = 0;
		int c = matrix.length - 1;
		int d = matrix[0].length - 1;
		while (a < c) {
			rotateEdge(matrix, a++, b++, c--, d--);
		}
	}

	public static void rotateEdge(int[][] m, int a, int b, int c, int d) {
		int tmp = 0;
		for (int i = 0; i < d - b; i++) {
			tmp = m[a][b + i];
			m[a][b + i] = m[c - i][b];
			m[c - i][b] = m[c][d - i];
			m[c][d - i] = m[a + i][d];
			m[a + i][d] = tmp;
		}
	}

	public static void printMatrix(int[][] matrix) {
		for (int i = 0; i != matrix.length; i++) {
			for (int j = 0; j != matrix[0].length; j++) {
				System.out.print(matrix[i][j] + " ");
			}
			System.out.println();
		}
	}

	public static void main(String[] args) {
		int[][] matrix = { { 1, 2, 3, 4 }, { 5, 6, 7, 8 }, { 9, 10, 11, 12 }, { 13, 14, 15, 16 } };
		printMatrix(matrix);
		rotate(matrix);
		System.out.println("=========");
		printMatrix(matrix);

	}

习题3 给定一个正方形或者长方形矩阵matrix，实现zigzag打印

0 1 2
3 4 5
6 7 8
打印: 0 1 3 6 4 2 5 7 8

public static void printMatrixZigZag(int[][] matrix) {
		int tR = 0;
		int tC = 0;
		int dR = 0;
		int dC = 0;
		int endR = matrix.length - 1;
		int endC = matrix[0].length - 1;
		boolean fromUp = false;
		while (tR != endR + 1) {
			printLevel(matrix, tR, tC, dR, dC, fromUp);
			tR = tC == endC ? tR + 1 : tR;
			tC = tC == endC ? tC : tC + 1;
			dC = dR == endR ? dC + 1 : dC;
			dR = dR == endR ? dR : dR + 1;
			fromUp = !fromUp;
		}
		System.out.println();
	}

	public static void printLevel(int[][] m, int tR, int tC, int dR, int dC, boolean f) {
		if (f) {
			while (tR != dR + 1) {
				System.out.print(m[tR++][tC--] + " ");
			}
		} else {
			while (dR != tR - 1) {
				System.out.print(m[dR--][dC++] + " ");
			}
		}
	}

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

	}

习题4 输入N,在控制台上输出初始边长为N的图案

public static void printStar(int N) {
		int leftUp = 0;
		int rightDown = N - 1;
		char[][] m = new char[N][N];
		for (int i = 0; i < N; i++) {
			for (int j = 0; j < N; j++) {
				m[i][j] = ' ';
			}
		}
		while (leftUp <= rightDown) {
			set(m, leftUp, rightDown);
			leftUp += 2;
			rightDown -= 2;
		}
		for (int i = 0; i < N; i++) {
			for (int j = 0; j < N; j++) {
				System.out.print(m[i][j] + " ");
			}
			System.out.println();
		}
	}

	public static void set(char[][] m, int leftUp, int rightDown) {
		for (int col = leftUp; col <= rightDown; col++) {
			m[leftUp][col] = '*';
		}
		for (int row = leftUp + 1; row <= rightDown; row++) {
			m[row][rightDown] = '*';
		}
		for (int col = rightDown - 1; col > leftUp; col--) {
			m[rightDown][col] = '*';
		}
		for (int row = rightDown - 1; row > leftUp + 1; row--) {
			m[row][leftUp + 1] = '*';
		}
	}

	public static void main(String[] args) {
		printStar(5);
	}