给定一个整型矩阵arr,按照转圈的方式打印
比如
输入:
4 4
1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16
输出:1 2 3 4 8 12 16 15 14 13 9 5 6 7 11 10
输入:
4 4
1 2 3 4
12 13 14 5
11 16 15 6
10 9 8 7
输出:1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
要求:额外的空间复杂度为O(1)
思路参考左程云,矩阵分圈处理方式。在矩阵中用左上角的坐标(startX, startY)和右下角的坐标(endX, endY)就可以表示一个子矩阵,比如例子中的矩阵,当(startX, startY)=(0, 0)时、(endX, endY)=(3, 3)时,表示的子矩阵就是整个矩阵,这个子矩阵的最外层如下:
1 2 3 4
5 8
9 12
13 14 15 16
如果能把这个子矩阵的外层转圈打印出来,那么就把startX, startY加1, 即(startX, startY) = (1, 1), 再把endX, endY减1,即(endX, endY) = (2, 2),此时表示子矩阵如下
6 7
10 11
将这个子矩阵转圈打印出来,接着把startX, startY加1, 即(startX, startY) = (2, 2), 再把endX, endY减1,即(endX, endY) = (1, 1),如果发现左上角坐标跑到了右下角坐标的右方或下方,整个过程就停止了。
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner cin = new Scanner(System.in);
int row = cin.nextInt();
int col = cin.nextInt();
int[][] arr = new int[row][col];
for (int i = 0; i < row; ++i) {
for (int j = 0; j < col; ++j) {
arr[i][j] = cin.nextInt();
}
}
cin.close();
orderPrint(arr);
}
private static void orderPrint(int[][] arr) {
int startX = 0, startY = 0;
int endX = arr.length - 1, endY = arr[0].length - 1;
while (startX <= endX && startY <= endY) {
print(arr, startX++, startY++, endX--, endY--);
}
}
private static void print(int[][] arr, int startX, int startY, int endX, int endY) {
if (startX == endX) { // 子矩阵只有一行
for (int i = startY; i <= endY; ++i) {
System.out.print(arr[startX][i] + " ");
}
} else if (startY == endY) { // 子矩阵只有一列
for (int i = startX; i <= endX; ++i) {
System.out.print(arr[i][startY] + " ");
}
} else {
int curX = startX;
int curY = startY;
while (curY != endY) {
System.out.print(arr[startX][curY++] + " ");
}
while (curX != endX) {
System.out.print(arr[curX++][endY] + " ");
}
while (curY != startY) {
System.out.print(arr[endX][curY--] + " ");
}
while (curX != startX) {
System.out.print(arr[curX--][startY] + " ");
}
}
}
}
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