Merge pull request #1660 from xiaoyu2018/master

分别添加0509、0070、0746、0062C#版本

problems/0062.不同路径.md

@@ -452,5 +452,25 @@ object Solution {
 }
 ```
 
+### c#
+
+```c#
+public class Solution
+{
+    public int UniquePaths(int m, int n)
+    {
+        int[] dp = new int[n];
+        for (int i = 0; i < n; i++)
+            dp[i] = 1;
+        for (int i = 1; i < m; i++)
+            for (int j = 1; j < n; j++)
+                dp[j] += dp[j - 1];
+        return dp[n - 1];
+    }
+}
+```
+
+
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0070.爬楼梯.md

@@ -425,5 +425,25 @@ object Solution {
 }
 ```
 
+### C#
+
+```c#
+public class Solution {
+    public int ClimbStairs(int n) {
+        if(n<=2) return n;
+        int[] dp = new int[2] { 1, 2 };
+        for (int i = 3; i <= n; i++)
+        {
+            int temp = dp[0] + dp[1];
+            dp[0] = dp[1];
+            dp[1] = temp;
+        }
+        return dp[1];
+    }
+}
+```
+
+
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0509.斐波那契数.md

@@ -370,5 +370,45 @@ object Solution {
 }
 ```
 
+### C#
+
+动态规划:
+
+```c#
+public class Solution
+{
+    public int Fib(int n)
+    {
+        if(n<2) return n;
+        int[] dp = new int[2] { 0, 1 };
+        for (int i = 2; i <= n; i++)
+        {
+            int temp = dp[0] + dp[1];
+            dp[0] = dp[1];
+            dp[1] = temp;
+        }
+        return dp[1];
+    }
+}
+```
+
+递归:
+
+```c#	
+public class Solution
+{
+    public int Fib(int n)
+    {
+        if(n<2)
+            return n;
+        return Fib(n-1)+Fib(n-2);
+    }
+}
+```
+
+
+
+
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>

problems/0746.使用最小花费爬楼梯.md

@@ -370,5 +370,26 @@ object Solution {
 }
 ```
 
+### C#
+
+```c#
+public class Solution
+{
+    public int MinCostClimbingStairs(int[] cost)
+    {
+        int[] dp=new int[2] { cost[0], cost[1] };
+        for (int i = 2; i < cost.Length; i++)
+        {
+            int temp = Math.Min(dp[0], dp[1])+cost[i];
+            dp[0]=dp[1];
+            dp[1]=temp;
+        }
+        return Math.Min(dp[0],dp[1]);
+    }
+}
+```
+
+
+
 -----------------------
 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>