SpiralMatrix

Change-Id: I286067954e3c6fe23dde7538a004bae96c810920

Author: applewjg

SpiralMatrix.java

@@ -0,0 +1,37 @@
+/*
+ Author:     King, [email protected]
+ Date:       Dec 25, 2014
+ Problem:    Spiral Matrix
+ Difficulty: Easy
+ Source:     https://oj.leetcode.com/problems/spiral-matrix/
+ Notes:
+ Given a matrix of m x n elements (m rows, n columns), return all elements of the matrix 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].
+
+ Solution: ...
+ */
+public class Solution {
+    public List<Integer> spiralOrder(int[][] matrix) {
+        ArrayList<Integer> res = new ArrayList<Integer>();
+        if (matrix.length == 0 || matrix[0].length == 0) return res;
+        int n = matrix.length, m = matrix[0].length, row = 0, col = -1;
+        while (true) {
+            for (int i = 0; i < m; ++i) res.add(matrix[row][++col]);
+            if (--n == 0) break;
+            for (int i = 0; i < n; ++i) res.add(matrix[++row][col]);
+            if (--m == 0) break;
+            for (int i = 0; i < m; ++i) res.add(matrix[row][--col]);
+            if (--n == 0) break;
+            for (int i = 0; i < n; ++i) res.add(matrix[--row][col]);
+            if (--m == 0) break;
+        }
+        return res;
+    }
+}

SpiralMatrixII.java

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+/*
+ Author:     King, [email protected]
+ Date:       Dec 25, 2014
+ Problem:    Spiral Matrix II
+ Difficulty: Easy
+ Source:     https://oj.leetcode.com/problems/spiral-matrix-ii/
+ Notes:
+ 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 ]
+ ]
+
+ Solution: ...
+ */
+ public class Solution {
+    public int[][] generateMatrix(int n) {
+        if (n <= 0) return new int[0][0];
+        int[][] res = new int[n][n];
+        int m = n, row = 0, col = -1, num = 0;
+        while (true) {
+            for (int i = 0; i < m; ++i) res[row][++col] = ++num;
+            if (--n == 0) break;
+            for (int i = 0; i < n; ++i) res[++row][col] = ++num;
+            if (--m == 0) break;
+            for (int i = 0; i < m; ++i) res[row][--col] = ++num;
+            if (--n == 0) break;
+            for (int i = 0; i < n; ++i) res[--row][col] = ++num;
+            if (--m == 0) break;
+        }
+        return res;
+    }
+}