Arrays-1 completed

Leetcode238.java

@@ -0,0 +1,21 @@
+// SC - O(1) since no extra space is being used
+// TC - O(n) Iteration of the array twice. 
+class Solution {
+    public int[] productExceptSelf(int[] nums) {
+        int[] res = new int[nums.length];
+        int suffixMul = nums[nums.length - 1];
+        int prefixMul = 1;
+        res[0] = prefixMul;
+        for (int i = 1; i < nums.length; i++) {
+            res[i] = nums[i - 1] * prefixMul; // res[i] will contain Mul till i-1
+            prefixMul = res[i]; // prefix mul 0 to i
+        }
+
+        for (int i = nums.length - 2; i >= 0; i--) {
+            res[i] = res[i] * suffixMul;// res[i] will contain Mul till i-1 and multiplied by suffix -> product of all
+                                        // items except ith element
+            suffixMul = nums[i] * suffixMul; // suffix mul from i to n
+        }
+        return res;
+    }
+}

Leetcode498.java

@@ -0,0 +1,45 @@
+// TC - O(m*n)
+// SC - O(1)
+class Solution {
+    public int[] findDiagonalOrder(int[][] mat) {
+        boolean top = true;
+        int m = mat.length;
+        int n = mat[0].length;
+        int[] res = new int[m * n];
+        int i = 0;
+        int r = 0;
+        int c = 0;
+
+        while (i < m * n) {
+
+            res[i] = mat[r][c];
+
+            if (top) {
+                if ((c + 1) >= n) {
+                    r = r + 1;
+                    top = false;
+                } else if ((r - 1) < 0) {
+                    c = c + 1;
+                    top = false;
+                } else {
+                    r = r - 1;
+                    c = c + 1;
+                }
+            } else {
+                if ((r + 1) >= m) {
+                    c = c + 1;
+                    top = true;
+                } else if ((c - 1) < 0) {
+                    r = r + 1;
+                    top = true;
+                } else {
+                    c = c - 1;
+                    r = r + 1;
+                }
+
+            }
+            i += 1;
+        }
+        return res;
+    }
+}

Leetcode54.java

@@ -0,0 +1,58 @@
+// TC  - O(mn)
+// SC - O(1)
+class Solution {
+    public List<Integer> spiralOrder(int[][] matrix) {
+        List<Integer> res = new ArrayList<>();
+
+        int top = 0;
+        int bottom = matrix.length - 1;
+        int left = 0;
+        int right = matrix[0].length - 1;
+
+        int i = 0; // Used to iterate resultant list
+        int r = 0; // Used to iterate intput matrix
+        int c = 0; // Used to iterate intput matrix
+
+        while (i < matrix.length * matrix[0].length) { // Use the max number of items possible to add into the array
+                                                       // instead of using boundaries.
+            while (c <= right) {
+                res.add(i, matrix[top][c]);
+                i += 1;
+                c += 1;
+            }
+            top += 1;
+            r = top;
+            while (r <= bottom) {
+                res.add(i, matrix[r][right]);
+                i += 1;
+                r += 1;
+            }
+            right -= 1;
+
+            c = right;
+            if (top <= bottom) {
+                while (c >= left) {
+                    res.add(i, matrix[bottom][c]);
+                    i += 1;
+                    c -= 1;
+                }
+                bottom -= 1;
+                r = bottom;
+            }
+
+            if (left <= right && top <= bottom) {
+                while (r >= top) {
+                    res.add(i, matrix[r][left]);
+                    i += 1;
+                    r -= 1;
+                }
+                left += 1;
+                c = left;
+
+            }
+
+        }
+        return res;
+
+    }
+}