Matrix Spiral Traverse Spiral matrix,spiral Matrix2

Spiralmatrix:

Given a matrix of m x n elements (m rows, n columns), return all elements of the Matri X in Spiral Order.

For example,
Given the following matrix:

[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

You should return [1,2,3,6,9,8,7,4,5] .

Algorithm analysis: In fact, is a double loop traversal, each time is a loop, and then traverse the inside a circle ..., need to record m,n, after each traversal, M,n minus 2, but also to record coordinates x, y;

The special case is n=1;m=1; in fact, M,n is odd.

public class Spiralmatrix {public list<integer> spiralorder (int[][] matrix) {list<integer> res = new Arraylist<> (); if (matrix.length = = 0 | | matrix = = NULL) {return res;} int m = Matrix.length;int n = matrix[0].length;//must first determine if the matrix is empty, otherwise the array subscript bounds int x = 0, y = 0;while (M > 0 && n > 0) {i F (m = = 1) {for (int i = 0; i < n; i + +) {Res.add (matrix[x][y++]);} break;//Don't forget break}else if (n = = 1) {for (int j = 0; J < m; J + +) {Res.add (matrix[x++][y]);} break;} for (int i = 0; i < n-1; i + +) {Res.add (matrix[x][y++]);} for (int i = 0; i < m-1; i + +) {Res.add (matrix[x++][y]);} for (int i = 0; i < n-1; i + +) {Res.add (matrix[x][y--]);} for (int i = 0; i < m-1; i + +) {Res.add (matrix[x--][y]);} X++;y++;m-= 2;n-= 2;} return res;}}

SPIRALMATRIX2:

Given an integer n, generate a square matrix filled with elements from 1 to n2 in Spiral order.

For example,
Given N = 3 ,

You should return the following matrix:

[[1, 2, 3], [8, 9, 4], [7, 6, 5]]

Algorithm analysis: And the previous algorithm, similar, but this is a n*n matrix, can actually extend to the m*n matrix. N*n makes emptying easier, especially when n=1.

public class SpiralMatrix2 {public int[][] Generatematrix (int n) {int[][] res = new Int[n][n];if (n = = 0) {return res;} int x = 0, y = 0;int val = 1;while (n > 0) {if (n = = 1) {Res[x][y] = val;break;} for (int i = 0; i < n-1; i + +) {res[x][y++] = Val;val + +;} for (int i = 0; i < n-1; i + +) {Res[x++][y] = Val;val + +;} for (int i = 0; i < n-1; i + +) {res[x][y--] = Val;val + +;} for (int i = 0; i < n-1; i + +) {Res[x--][y] = Val;val + +;} X ++;y ++;n-= 2;} return res;}}

Matrix Spiral Traverse Spiral matrix,spiral Matrix2