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PrintMatrix.java

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import java.util.ArrayList;

/**

* 剑指Offer，顺时针打印矩阵

*/

public class PrintMatrix {

public static void main(String[] args) {

int[][] matrix = {

{1, 2, 3, 4, 5}

};

ArrayList<Integer> list = printMatrix(matrix);

for (int i : list) {

System.out.print(i + " ");

}

}

public static ArrayList<Integer> printMatrix(int [][] matrix) {

if (matrix == null || matrix.length == 0) {

return null;

}

ArrayList<Integer> result = new ArrayList<>();

int up = 0, left = 0, down = matrix.length - 1, right = matrix[0].length - 1;

while (left <= right && up <= down) {

// 从左到右打印一行

for (int i = left; i <= right; i++) {

result.add(matrix[up][i]);

}

up++;

// 从上到下打印一列

for (int i = up; i <= down; i++) {

result.add(matrix[i][right]);

}

right--;

// 从右到左打印一行

for (int i = right; i >= left && up <= down; i--) {

result.add(matrix[down][i]);

}

down--;

// 从下到上打印一列

for (int i = down; i >= up && left <= right; i--) {

result.add(matrix[i][left]);

}

left++;

}

return result;

}

}