interviews/leetcode/array/SpiralMatrix.java at master · codingOnGithub/interviews · GitHub

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//Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix in 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]

class SpiralMatrix {

public List<Integer> spiralOrder(int[][] matrix) {

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

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

return result;

}

int rowStart = 0;

int rowEnd = matrix.length - 1;

int colStart = 0;

int colEnd = matrix[0].length - 1;

while(rowStart <= rowEnd && colStart <= colEnd) {

for(int i = colStart; i <= colEnd; i++) {

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

}

rowStart++;

for(int i = rowStart; i <= rowEnd; i++) {

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

}

colEnd--;

if(rowStart <= rowEnd) {

for(int i = colEnd; i >= colStart; i--) {

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

}

rowEnd--;

if(colStart <= colEnd) {

for(int i = rowEnd; i >= rowStart; i--) {

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

}

colStart++;

}

return result;

}

interviews/leetcode/array/SpiralMatrix.java at master · codingOnGithub/interviews · GitHub

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