杨辉三角

Author: uuk020

pascals_triangle/pascals_triangle.php

@@ -0,0 +1,42 @@
+<?php
+/**
+ * pascals_triangle 以数组形式输出杨辉三角
+ * Write a function that, given a depth (n), returns a single-dimensional array representing Pascal's Triangle to the n-th level.
+ * @param    [type] $n 几项
+ * @return   [array]
+ */
+function pascals_triangle($n)
+{
+  // Your code here
+  $orginArr = [1];
+  if ($n == 1) return $orginArr;
+  $tmp = $orginArr;
+  array_push($orginArr, 1);
+  $result = array_merge($tmp, $orginArr);
+  if ($n == 2) return $result;
+  $row = 2;
+  // 循环$n大于2的情况
+  while ($row <= $n - 1) {
+       $oldArr         = $orginArr;
+       $orginArr[$row] = 1;
+       $row++;
+       for ($i = 1; $i < count($oldArr); $i++) {
+            $orginArr[$i] = $oldArr[$i] + $oldArr[$i - 1];
+       }
+       $result = array_merge($result, $orginArr);
+  }
+  return $result;
+}
+// 以数组形式输出杨辉三角 聪明的办法
+function pascals_triangle_clever($n)
+{
+    $pascal = [];
+    for ($i = 0; $i < $n; $i++) {
+        $num = 1;
+        for ($j = 0; $j <= $i; $j++) {
+            array_push($pascal, $num);
+            $num = $num * ($i - $j) / ($j + 1);
+        }
+    }
+    return $pascal;
+}