feat: add the solution of Pascal's Triangle II(119) with kotlin.

Author: relish-wang

README.md

@@ -56,7 +56,7 @@
 | [111][111-question] | [Minimum Depth of Binary Tree][111-tips]                     | [✅][111-java] |              | [✅][111-kotlin] |
 | [112][112-question] | [Path Sum][112-tips]                                         | [✅][112-java] |              | [✅][112-kotlin] |
 | [118][118-question] | [Pascal's Triangle][118-tips]                                | [✅][118-java] |              | [✅][118-kotlin] |
-| [119][119-question] | [Pascal's Triangle II][119-tips]                             | [✅][119-java] |              |                  |
+| [119][119-question] | [Pascal's Triangle II][119-tips]                             | [✅][119-java] |              | [✅][119-kotlin] |
 | [121][121-question] | [Best Time to Buy and Sell Stock][121-tips]                  | [✅][121-java] |              |                  |
 | [122][122-question] | [Best Time to Buy and Sell Stock II][122-tips]               | [✅][122-java] |              |                  |
 | [226][226-question] | [Invert Binary Tree][226-tips]                               | [✅][226-java] | [✅][226-js] |                  |
@@ -512,4 +512,5 @@
 [111-kotlin]: ./src/_111/kotlin/Solution.kt
 [112-kotlin]: ./src/_112/kotlin/Solution.kt
 [118-kotlin]: ./src/_118/kotlin/Solution.kt
+[119-kotlin]: ./src/_119/kotlin/Solution.kt
 [771-kotlin]: ./src/_771/kotlin/Solution.kt

src/_118/kotlin/Solution.kt

@@ -24,5 +24,10 @@ class Solution {
 }
 
 fun main(args: Array<String>) {
-    println(Solution().generate(7))
-}
+    val message = Solution().generate(10)
+    for(item in message){
+        println(item)
+    }
+}
+//2 3 4 5 6 7 8
+//3 6 10 15 21 28

src/_119/kotlin/Solution.kt

@@ -0,0 +1,38 @@
+package _119.kotlin
+
+/**
+ * @author relish
+ * @since 2018/05/05
+ */
+class Solution {
+    fun getRow1(rowIndex: Int): List<Int> {
+        val list = Array(rowIndex + 1, { i -> Array(i + 1, { 1 }) })
+        for (i in 0 until rowIndex + 1) {
+            for (j in 0 until i) {
+                if (j == 0 || j == i) {
+                    list[i][j] = 1
+                } else {
+                    list[i][j] = list[i - 1][j - 1] + list[i - 1][j]
+                }
+            }
+        }
+        return list[rowIndex].asList()
+    }
+
+    fun getRow(rowIndex: Int): List<Int> {
+        val res = Array(rowIndex + 1, { 1 })
+        for (i in 1 until rowIndex + 1) {
+            if (i > (rowIndex + 1) / 2) {
+                res[i] = res[rowIndex - i]
+                continue
+            }
+            res[i] = ((res[i - 1]) * (rowIndex - i + 1).toLong() / i).toInt()
+        }
+        return res.asList()
+    }
+}
+
+fun main(args: Array<String>) {
+    println(Solution().getRow(3))
+    println(Solution().getRow(30))
+}

tips/119/README.md

@@ -15,10 +15,11 @@ Could you optimize your algorithm to use only *O*(*k*) extra space?
 **Tags:** Array
 
 
-## 思路
+## 思路0
 
 题意是指定输出帕斯卡尔三角形的某一行，模拟即可，优化后的代码如下所示。
 
+java:
 ```java
 class Solution {
     public List<Integer> getRow(int rowIndex) {
@@ -33,7 +34,25 @@ class Solution {
     }
 }
 ```
+## 思路1
 
+题目提示我们可以思考一下时间复杂度为O(n)的算法。仔细观察每一行数字即可找出规律。 
+kotlin(184ms/66.67%):
+```kotlin
+class Solution {
+    fun getRow(rowIndex: Int): List<Int> {
+        val res = Array(rowIndex + 1, { 1 })
+        for (i in 1 until rowIndex + 1) {
+            if (i > (rowIndex + 1) / 2) {
+                res[i] = res[rowIndex - i]
+                continue
+            }
+            res[i] = ((res[i - 1]) * (rowIndex - i + 1).toLong() / i).toInt()
+        }
+        return res.asList()
+    }
+}
+```
 
 ## 结语