Merge pull request #1484 from wzqwtt/dp01

添加（0509.斐波那契数、0070.爬楼梯、0746.使用最小花费爬楼梯） Scala版本

problems/0070.爬楼梯.md

@@ -401,6 +401,38 @@ int climbStairs(int n){
 }
 ```
 
+### Scala
+
+```scala
+object Solution {
+  def climbStairs(n: Int): Int = {
+    if (n <= 2) return n
+    var dp = new Array[Int](n + 1)
+    dp(1) = 1
+    dp(2) = 2
+    for (i <- 3 to n) {
+      dp(i) = dp(i - 1) + dp(i - 2)
+    }
+    dp(n)
+  }
+}
+```
+
+优化空间复杂度:
+```scala
+object Solution {
+  def climbStairs(n: Int): Int = {
+    if (n <= 2) return n
+    var (a, b) = (1, 2)
+    for (i <- 3 to n) {
+      var tmp = a + b
+      a = b
+      b = tmp
+    }
+    b // 最终返回b
+  }
+}
+```
 
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