Leetcode [54] (Java): Spiral Matrix

title : Spiral Matrix

Difficulty : Medium

topic content :

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

translation :

Given a matrix of M x n elements (m rows, n columns), all elements of the matrix are returned in a clockwise spiral order.

Example 1:

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

Example 2:

input:[  [1, 2, 3, 4],  [5, 6, 7, 8],  [9,10,11,12]]output: [1,2,3,4,8,12,11,10,9,5,6,7]

my idea : Because every lap is composed of four sides, so write a while dead loop, inside there are four for loops, each for the end of the corresponding indicator will be reduced, at the same time to determine whether exceeding the standard, the exit.

eg

while (true) {

Sideways for add

Top + +

Whether top is less than bottom is the break

。。。

｝

My Code :

1      PublicList<integer> Spiralorder (int[] matrix) {2list<integer> res =NewArraylist<integer>();3         if(Matrix.length = = 0 | | matrix[0].length = = 0)returnRes;4         5         inttop = 0;6         intBottom = Matrix.length-1;7         intleft = 0;8         intright = Matrix[0].length-1;9         Ten          while(true){ One              for(inti = left; I <= right; i++) Res.add (Matrix[top][i]); Atop++; -             if(Left > Right | | top > Bottom) Break; -              the              for(inti = top; I <= bottom; i++) Res.add (Matrix[i][right]); -right--; -             if(Left > Right | | top > Bottom) Break; -              +              for(inti = right; I >= left; i--) Res.add (Matrix[bottom][i]); -bottom--; +             if(Left > Right | | top > Bottom) Break; A              at              for(inti = bottom; I >= top; i--) Res.add (Matrix[i][left]); -left++; -             if(Left > Right | | top > Bottom) Break; -         } -          -         returnRes; in}

my complexity : O (N * M) rows multiplied by columns

problems in the encoding process :

1, did not notice that when the input is an empty array, right and bottom will be negative, so we have to add a sentence empty.

Answer code :

The same as me.

Leetcode [54] (Java): Spiral Matrix