Create diagonal-traverse-ii.cpp

Author: kamyu104

C++/diagonal-traverse-ii.cpp

@@ -0,0 +1,54 @@
+// Time:  O(m * n)
+// Space: O(m)
+
+class Solution {
+public:
+    vector<int> findDiagonalOrder(vector<vector<int>>& nums) {
+        const auto& n = accumulate(nums.cbegin(), nums.cend(), uint64_t(0ull),
+                                   [](const auto& x, const auto& y) {
+                                       return max(x, y.size());
+                                   });
+        vector<int> result;
+        vector<pair<int, int>> q;
+        for (int r = 0; r < nums.size() + n - 1; ++r) {
+            vector<pair<int, int>> new_q;
+            if (r < nums.size()) {
+                q.emplace_back(r, 0);
+            }
+            for (int i = q.size() - 1; i >= 0; --i) {
+                const auto& [r, c] = q[i];
+                result.emplace_back(nums[r][c]);
+                if (c + 1 < nums[r].size()) {
+                    new_q.emplace_back(r, c + 1);
+                }
+            }
+            reverse(new_q.begin(), new_q.end());
+            q = move(new_q);
+        }
+        return result;
+    }
+};
+
+// Time:  O(m * n)
+// Space: O(m * n)
+class Solution2 {
+public:
+    vector<int> findDiagonalOrder(vector<vector<int>>& nums) {
+        vector<vector<int>> ans;
+        for (int r = 0; r < nums.size(); ++r) {
+            for (int c = 0; c < nums[r].size(); ++c) {
+                if (ans.size() <= r + c) {
+                    ans.emplace_back();
+                }
+                ans[r + c].emplace_back(nums[r][c]);
+            }
+        }
+        vector<int> result;
+        for (const auto& row: ans) {
+            for (int i = row.size() - 1; i >= 0; --i) {
+                result.emplace_back(row[i]);
+            }
+        }
+        return result;
+    }
+};