From 8ed5e92d5f58d4d91ccd58cd01bb11eca367137c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E5=94=90=E6=A0=91=E6=A3=AE?= <14021051@buaa.edu.cn>
Date: Sun, 2 Sep 2018 16:08:54 +0800
Subject: [PATCH] Create 119. Pascal's Triangle II.md

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+# [119. Pascal's Triangle II](https://leetcode.com/problems/pascals-triangle-ii/description/)
+# 思路
+类似第118题，不过这里要求只输出第rowIndex行，而且尽量使用O(k)的空间。  
+我们可以依次迭代计算第0、第1...第rowIndex行结果，这是最外层循环，  
+在得到第i-1行结果时，可以从前往后依次更新数组里的值来得到第i行的结果，这是内层循环。  
+注意用一个pre来记录第i-1行里面第j个元素的前一个元素的值。
+# C++
+```
+class Solution {
+public:
+    vector<int> getRow(int rowIndex) {
+        vector<int>result(rowIndex + 1);
+        result[0] = 1;
+        for(int i = 1; i <= rowIndex; i++){
+            int tmp, pre = result[0];
+            for(int j = 1; j < i; j++){
+                tmp = result[j];
+                result[j] += pre;
+                pre = tmp;
+            }
+            result[i] = 1;
+        }
+        return result;          
+    }
+};
+```