Pascals triangle done

Author: rampatra

src/main/java/com/leetcode/arrays/PascalsTriangle.java

@@ -0,0 +1,52 @@
+package com.leetcode.arrays;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Problem: https://leetcode.com/problems/pascals-triangle/
+ *
+ * @author rampatra
+ * @since 2019-04-20
+ */
+public class PascalsTriangle {
+
+    /**
+     * Time complexity: O(numRows^2)
+     * Space complexity: O(numRows^2)
+     * <p>
+     * Runtime: <a href="https://leetcode.com/submissions/detail/223784377/">0 ms</a>.
+     *
+     * @param numRows
+     * @return
+     */
+    public static List<List<Integer>> generatePascalsTriangle(int numRows) {
+        List<List<Integer>> pascalsTriangle = new ArrayList<>();
+
+        if (numRows == 0) return pascalsTriangle;
+
+        List<Integer> firstRow = new ArrayList<>();
+        firstRow.add(1);
+        pascalsTriangle.add(firstRow);
+
+        List<Integer> prevRow;
+        for (int i = 1; i < numRows; i++) {
+            prevRow = pascalsTriangle.get(i - 1);
+
+            List<Integer> currRow = new ArrayList<>();
+            currRow.add(1);
+            for (int j = 0; j < prevRow.size() - 1; j++) {
+                currRow.add(prevRow.get(j) + prevRow.get(j + 1));
+            }
+            currRow.add(1);
+
+            pascalsTriangle.add(currRow);
+        }
+
+        return pascalsTriangle;
+    }
+
+    public static void main(String[] args) {
+        System.out.println(generatePascalsTriangle(5));
+    }
+}