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杨辉三角

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	`1`	`+<?php`
	`2`	`+/**`
	`3`	`+ * pascals_triangle 以数组形式输出杨辉三角`
	`4`	`+ * Write a function that, given a depth (n), returns a single-dimensional array representing Pascal's Triangle to the n-th level.`
	`5`	`+ * @param [type] $n 几项`
	`6`	`+ * @return [array]`
	`7`	`+ */`
	`8`	`+function pascals_triangle($n)`
	`9`	`+{`
	`10`	`+ // Your code here`
	`11`	`+ $orginArr = [1];`
	`12`	`+ if ($n == 1) return $orginArr;`
	`13`	`+ $tmp = $orginArr;`
	`14`	`+ array_push($orginArr, 1);`
	`15`	`+ $result = array_merge($tmp, $orginArr);`
	`16`	`+ if ($n == 2) return $result;`
	`17`	`+ $row = 2;`
	`18`	`+ // 循环$n大于2的情况`
	`19`	`+ while ($row <= $n - 1) {`
	`20`	`+ $oldArr = $orginArr;`
	`21`	`+ $orginArr[$row] = 1;`
	`22`	`+ $row++;`
	`23`	`+ for ($i = 1; $i < count($oldArr); $i++) {`
	`24`	`+ $orginArr[$i] = $oldArr[$i] + $oldArr[$i - 1];`
	`25`	`+ }`
	`26`	`+ $result = array_merge($result, $orginArr);`
	`27`	`+ }`
	`28`	`+ return $result;`
	`29`	`+}`
	`30`	`+// 以数组形式输出杨辉三角聪明的办法`
	`31`	`+function pascals_triangle_clever($n)`
	`32`	`+{`
	`33`	`+ $pascal = [];`
	`34`	`+ for ($i = 0; $i < $n; $i++) {`
	`35`	`+ $num = 1;`
	`36`	`+ for ($j = 0; $j <= $i; $j++) {`
	`37`	`+ array_push($pascal, $num);`
	`38`	`+ $num = $num * ($i - $j) / ($j + 1);`
	`39`	`+ }`
	`40`	`+ }`
	`41`	`+ return $pascal;`
	`42`	`+}`

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