Added solution for spiral matrix.

anxious-coder-lhs · anxious-coder-lhs · commit ffd5540fe182 · 2020-11-05T12:53:11.000+05:30
diff --git a/README.md b/README.md
@@ -52,6 +52,7 @@ Happy to accept any contributions to this in any langugage.
 17. [Leet Code 554 Brick Wall](https://leetcode.com/problems/brick-wall/) | [Solution 1](./level_medium/LeetCode_554_Brick_Wall_Medium.ts)
 18. [Leet Code 1190 Reverse Substrings Between Each Pair of Paranthesis](https://leetcode.com/problems/reverse-substrings-between-each-pair-of-parentheses/) | [Solution 1](level_medium/LeetCode_1190_Reverse_Substrings.ts) | [Solution Optimized](level_medium/LeetCode_1190_Reverse_Substrings_1.ts)
 19. [Leet Code 22 Generate Paranthesis](https://leetcode.com/problems/generate-parentheses/) | [Solution Brute Force](level_medium/LeetCode_22_Generate_Paranthesis_1.ts) | [Solution BF Optimized](level_medium/LeetCode_22_Generate_Paranthesis_2.ts)
+20. [Leet Code 54 Spiral Matrix] | [Solution](./med/../level_medium/SpiralMatrix.ts)
 
 
 ## Hard
diff --git a/level_medium/SpiralMatrix.ts b/level_medium/SpiralMatrix.ts
@@ -0,0 +1,42 @@
+/**
+ * Problem: LeetCode 54
+ * Solution: Uses Multiple pointer approach. Marks the boundaries of the entire array using a row boundary marker
+ * and the col boundary markers. Continue to iterate the matrix at the boundary conditions. Keep moving and squeezing
+ * the boundary conditions inwards.
+ * 
+ * Complexity: Time O(n) since all the elements are traversed exactly once. Space: O(n) since all the elements
+ * are stored once.
+ * 
+ * @param matrix 
+ */
+function spiralOrder(matrix: number[][]): number[] {
+    
+    if (matrix.length === 0 || matrix[0].length === 0) return []
+    
+    let rowEnd = matrix.length - 1, rowBeg = 0;
+    let colEnd = matrix[0].length - 1, colBeg = 0;
+    
+    const result: number[] = []
+    
+    // Continue till the bounds are within the range.
+    while(rowEnd >= rowBeg && colEnd >= colBeg) {
+        // Add values from horizontal top
+        for (let col = colBeg; col <= colEnd; col++) result.push(matrix[rowBeg][col])
+        
+        // Add values from vertical right
+        for (let row = rowBeg + 1; row <= rowEnd; row++) result.push(matrix[row][colEnd])
+        
+        // Add values from horizontal bottom
+        if (rowBeg !== rowEnd)
+            for (let col = colEnd - 1; col >= colBeg; col--) result.push(matrix[rowEnd][col])
+        
+        // Add values from vertical left
+        if (colBeg !== colEnd)
+            for (let row = rowEnd - 1; row > rowBeg; row--) result.push(matrix[row][colBeg])
+
+        // Squeeze
+        rowEnd--; rowBeg++; colEnd--; colBeg++;
+    }
+    
+    return result;
+};
