Merge pull request #29 from fartem/118_Pascal's_Triangle

2023-02-20 update: added "118. Pascal's Triangle"

Author: fartem

README.md

@@ -37,3 +37,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 110. Balanced Binary Tree                       | [Link](https://leetcode.com/problems/balanced-binary-tree/)                       | [Link](./lib/easy/balanced_binary_tree.dart)                       |
 | 111. Minimum Depth of Binary Tree               | [Link](https://leetcode.com/problems/minimum-depth-of-binary-tree/)               | [Link](./lib/easy/minimum_depth_of_binary_tree.dart)               |
 | 112. Path Sum                                   | [Link](https://leetcode.com/problems/path-sum/)                                   | [Link](./lib/easy/path_sum.dart)                                   |
+| 118. Pascal's Triangle                          | [Link](https://leetcode.com/problems/pascals-triangle/)                           | [Link](./lib/easy/pascals_triangle.dart)                           |

lib/easy/pascals_triangle.dart

@@ -0,0 +1,21 @@
+// https://leetcode.com/problems/pascals-triangle/
+class Solution {
+  List<List<int>> generate(int numRows) {
+    var result = <List<int>>[];
+    result.add([1]);
+    for (int i = 1; i < numRows; i++) {
+      var row = List.generate(i + 1, (_) => 0);
+      row[0] = 1;
+      row[row.length - 1] = 1;
+      if (i >= 2) {
+        var prev = result[i - 1];
+        var p = 1;
+        for (var j = 0; j < prev.length - 1; j++) {
+          row[p++] = prev[j] + prev[j + 1];
+        }
+      }
+      result.add(row);
+    }
+    return result;
+  }
+}

test/easy/pascals_triangle_test.dart

@@ -0,0 +1,33 @@
+import 'package:leetcode_dart/easy/pascals_triangle.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group(
+    'Example tests',
+    () {
+      final pt = Solution();
+      test(
+        '[[1], [1, 1], [1, 2, 1], [1, 3, 3, 1], [1, 4, 6, 4, 1]]',
+        () => expect(
+          [
+            [1],
+            [1, 1],
+            [1, 2, 1],
+            [1, 3, 3, 1],
+            [1, 4, 6, 4, 1],
+          ],
+          pt.generate(5),
+        ),
+      );
+      test(
+        '[1]',
+        () => expect(
+          [
+            [1],
+          ],
+          pt.generate(1),
+        ),
+      );
+    },
+  );
+}