feat: add solutions to lc problem: No.0091. Decode Ways

Author: yanglbme

README.md

@@ -180,9 +180,9 @@
 - [单词拆分](./solution/0100-0199/0139.Word%20Break/README.md)
 - [接雨水](./solution/0000-0099/0042.Trapping%20Rain%20Water/README.md)
 - [等差数列划分](./solution/0400-0499/0413.Arithmetic%20Slices/README.md)
+- [解码方法](./solution/0000-0099/0091.Decode%20Ways/README.md)
 - [礼物的最大价值](./lcof/面试题47.%20礼物的最大价值/README.md)
 - [最小路径和](./solution/0000-0099/0064.Minimum%20Path%20Sum/README.md)
-- [解码方法](./solution/0000-0099/0091.Decode%20Ways/README.md)
 - [最长上升子序列](./solution/0300-0399/0300.Longest%20Increasing%20Subsequence/README.md)
 - [俄罗斯套娃信封问题](./solution/0300-0399/0354.Russian%20Doll%20Envelopes/README.md)
 - [最长公共子序列](./solution/1100-1199/1143.Longest%20Common%20Subsequence/README.md)

README_EN.md

@@ -174,8 +174,8 @@ Complete solutions to [LeetCode](https://leetcode.com/problemset/all/), [LCOF](h
 - [Word Break](./solution/0100-0199/0139.Word%20Break/README_EN.md)
 - [Trapping Rain Water](./solution/0000-0099/0042.Trapping%20Rain%20Water/README_EN.md)
 - [Arithmetic Slices](./solution/0400-0499/0413.Arithmetic%20Slices/README_EN.md)
-- [Minimum Path Sum](./solution/0000-0099/0064.Minimum%20Path%20Sum/README_EN.md)
 - [Decode Ways](./solution/0000-0099/0091.Decode%20Ways/README_EN.md)
+- [Minimum Path Sum](./solution/0000-0099/0064.Minimum%20Path%20Sum/README_EN.md)
 - [Longest Increasing Subsequence](./solution/0300-0399/0300.Longest%20Increasing%20Subsequence/README_EN.md)
 - [Russian Doll Envelopes](./solution/0300-0399/0354.Russian%20Doll%20Envelopes/README_EN.md)
 - [Longest Common Subsequence](./solution/1100-1199/1143.Longest%20Common%20Subsequence/README_EN.md)

solution/0000-0099/0091.Decode Ways/README.md

@@ -173,6 +173,81 @@ class Solution {
 }
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    int numDecodings(string s) {
+        int n = s.size();
+        vector<int> dp(n + 1);
+        dp[0] = 1;
+        for (int i = 1; i <= n; ++i) {
+            if (s[i - 1] != '0') {
+                dp[i] += dp[i - 1];
+            }
+            if (i > 1 && s[i - 2] != '0') {
+                if ((s[i - 2] - '0') * 10 + s[i - 1] - '0' <= 26) {
+                    dp[i] += dp[i - 2];
+                }
+            }
+        }
+        return dp[n];
+    }
+};
+```
+
+### **Go**
+
+```go
+func numDecodings(s string) int {
+	n := len(s)
+	dp := make([]int, n+1)
+	dp[0] = 1
+	for i := 1; i <= n; i++ {
+		if s[i-1] != '0' {
+			dp[i] += dp[i-1]
+		}
+		if i > 1 && s[i-2] != '0' {
+			if (s[i-2]-'0')*10+(s[i-1]-'0') <= 26 {
+				dp[i] += dp[i-2]
+			}
+		}
+	}
+	return dp[n]
+}
+```
+
+### **C#**
+
+```cs
+public class Solution {
+    public int NumDecodings(string s) {
+        if (s.Length == 0) return 0;
+        
+        var f0 = 1;
+        var f1 = 1;
+        var f2 = 1;
+        for (var i = 0; i < s.Length; ++i)
+        {
+            f0 = f1;
+            f1 = f2;
+            f2 = 0;
+            var two = i > 0 ? int.Parse(string.Format("{0}{1}", s[i - 1], s[i])) : 0;
+            if (two >= 10 && two <= 26)
+            {
+               f2 += f0;  
+            }
+            if (s[i] != '0')
+            {
+                f2 += f1;
+            }
+        }
+        return f2;
+    }
+}
+```
+
 ### **...**
 
 ```

solution/0000-0099/0091.Decode Ways/README_EN.md

@@ -72,6 +72,8 @@ Hence, there are no valid ways to decode this since all digits need to be mapped
 
 ## Solutions
 
+Dynamic programming.
+
 <!-- tabs:start -->
 
 ### **Python3**
@@ -155,6 +157,81 @@ class Solution {
 }
 ```
 
+### **C++**
+
+```cpp
+class Solution {
+public:
+    int numDecodings(string s) {
+        int n = s.size();
+        vector<int> dp(n + 1);
+        dp[0] = 1;
+        for (int i = 1; i <= n; ++i) {
+            if (s[i - 1] != '0') {
+                dp[i] += dp[i - 1];
+            }
+            if (i > 1 && s[i - 2] != '0') {
+                if ((s[i - 2] - '0') * 10 + s[i - 1] - '0' <= 26) {
+                    dp[i] += dp[i - 2];
+                }
+            }
+        }
+        return dp[n];
+    }
+};
+```
+
+### **Go**
+
+```go
+func numDecodings(s string) int {
+	n := len(s)
+	dp := make([]int, n+1)
+	dp[0] = 1
+	for i := 1; i <= n; i++ {
+		if s[i-1] != '0' {
+			dp[i] += dp[i-1]
+		}
+		if i > 1 && s[i-2] != '0' {
+			if (s[i-2]-'0')*10+(s[i-1]-'0') <= 26 {
+				dp[i] += dp[i-2]
+			}
+		}
+	}
+	return dp[n]
+}
+```
+
+### **C#**
+
+```cs
+public class Solution {
+    public int NumDecodings(string s) {
+        if (s.Length == 0) return 0;
+        
+        var f0 = 1;
+        var f1 = 1;
+        var f2 = 1;
+        for (var i = 0; i < s.Length; ++i)
+        {
+            f0 = f1;
+            f1 = f2;
+            f2 = 0;
+            var two = i > 0 ? int.Parse(string.Format("{0}{1}", s[i - 1], s[i])) : 0;
+            if (two >= 10 && two <= 26)
+            {
+               f2 += f0;  
+            }
+            if (s[i] != '0')
+            {
+                f2 += f1;
+            }
+        }
+        return f2;
+    }
+}
+```
+
 ### **...**
 
 ```

solution/0000-0099/0091.Decode Ways/Solution.cpp

@@ -0,0 +1,19 @@
+class Solution {
+public:
+    int numDecodings(string s) {
+        int n = s.size();
+        vector<int> dp(n + 1);
+        dp[0] = 1;
+        for (int i = 1; i <= n; ++i) {
+            if (s[i - 1] != '0') {
+                dp[i] += dp[i - 1];
+            }
+            if (i > 1 && s[i - 2] != '0') {
+                if ((s[i - 2] - '0') * 10 + s[i - 1] - '0' <= 26) {
+                    dp[i] += dp[i - 2];
+                }
+            }
+        }
+        return dp[n];
+    }
+};

solution/0000-0099/0091.Decode Ways/Solution.go

@@ -0,0 +1,16 @@
+func numDecodings(s string) int {
+	n := len(s)
+	dp := make([]int, n+1)
+	dp[0] = 1
+	for i := 1; i <= n; i++ {
+		if s[i-1] != '0' {
+			dp[i] += dp[i-1]
+		}
+		if i > 1 && s[i-2] != '0' {
+			if (s[i-2]-'0')*10+(s[i-1]-'0') <= 26 {
+				dp[i] += dp[i-2]
+			}
+		}
+	}
+	return dp[n]
+}