finish 54

Author: BaffinLee

54. Spiral Matrix.js

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+/**
+ * 54. Spiral Matrix
+ * 
+ * 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]
+ */
+
+/**
+ * @param {number[][]} matrix
+ * @return {number[]}
+ */
+var spiralOrder = function(matrix) {
+	var n = matrix.length;
+	var m = (matrix[0] || []).length;
+	var res = [];
+	var x1 = 0;
+	var x2 = m - 1;
+	var y1 = 0;
+	var y2 = n - 1;
+	while (x1 <= x2 && y1 <= y2) {
+		for (var x = x1; x <= x2; x++) res.push(matrix[y1][x]);
+		for (var y = y1 + 1; y <= y2; y++) res.push(matrix[y][x2]);
+		if (x1 < x2 && y1 < y2) {
+			for (var x = x2 - 1; x > x1; x--) res.push(matrix[y2][x]);
+			for (var y = y2; y > y1; y--) res.push(matrix[y][x1]);
+		}
+		x1++;
+		x2--;
+		y1++;
+		y2--;
+	}
+	return res;
+};
+
+// 横的当做 x 轴，竖的当 y 轴
+// x1、x2、y1、y2 是当前遍历的四边形的四个角