feat: add solutions to lcof problem: No.46

Author: yanglbme

lcof/面试题46. 把数字翻译成字符串/README.md

@@ -1,28 +1,17 @@
 class Solution {
 public:
     int translateNum(int num) {
-        // string s = to_string(num);
-        // int n = s.size();
-        // vector<int> dp(n + 1);
-        // dp[0] = dp[1] = 1;
-        // for (int i = 2; i <= n; ++i) {
-        //     dp[i] = dp[i - 1];
-        //     if (s[i - 2] == '1' || s[i - 2] == '2' && s[i - 1] < '6') {
-        //         dp[i] += dp[i - 2];
-        //     }
-        // }
-        // return dp[n];
         string s = to_string(num);
         int n = s.size();
-        int dp_0 = 1, dp_1 = 1, dp_2 = 1;
-        for (int i = 2; i <= n; ++i) {
-            dp_2 = dp_1;
-            if (s[i - 2] == '1' || s[i - 2] == '2' && s[i - 1] < '6') {
-                dp_2 += dp_0;
+        int a = 1, b = 1;
+        for (int i = 1; i < n; ++i) {
+            int c = b;
+            if (s[i - 1] == '1' || (s[i - 1] == '2' && s[i] < '6')) {
+                c += a;
             }
-            dp_0 = dp_1;
-            dp_1 = dp_2;
+            a = b;
+            b = c;
         }
-        return dp_2;
+        return b;
     }
-};
+};

lcof/面试题46. 把数字翻译成字符串/Solution.cpp

@@ -1,13 +1,16 @@
 public class Solution {
     public int TranslateNum(int num) {
-        return TranslateString(num.ToString());
-    }
-
-    private int TranslateString(string s) {
-        if (s.Length < 2) {
-            return 1;
+        var s = num.ToString();
+        int n = s.Length;
+        int a = 1, b = 1;
+        for (int i = 1; i < n; ++i) {
+            int c = b;
+            if (s[i - 1] == '1' || (s[i - 1] == '2' && s[i] < '6')) {
+                c += a;
+            }
+            a = b;
+            b = c;
         }
-        int t = int.Parse(s[..2]);
-        return t < 10 || t > 25 ? TranslateString(s[1..]) : TranslateString(s[1..]) + TranslateString(s[2..]);
+        return b;
     }
 }

lcof/面试题46. 把数字翻译成字符串/Solution.cs

@@ -0,0 +1,13 @@
+func translateNum(num int) int {
+	s := strconv.Itoa(num)
+	n := len(s)
+	a, b := 1, 1
+	for i := 1; i < n; i++ {
+		c := b
+		if s[i-1] == '1' || (s[i-1] == '2' && s[i] < '6') {
+			c += a
+		}
+		a, b = b, c
+	}
+	return b
+}

lcof/面试题46. 把数字翻译成字符串/Solution.go

@@ -1,14 +1,16 @@
 class Solution {
     public int translateNum(int num) {
-        return cal(String.valueOf(num));
-    }
-
-    private int cal(String s) {
-        int n = s.length();
-        if (n < 2) {
-            return 1;
+        char[] s = String.valueOf(num).toCharArray();
+        int n = s.length;
+        int a = 1, b = 1;
+        for (int i = 1; i < n; ++i) {
+            int c = b;
+            if (s[i - 1] == '1' || (s[i - 1] == '2' && s[i] < '6')) {
+                c += a;
+            }
+            a = b;
+            b = c;
         }
-        int t = Integer.parseInt(s.substring(0, 2));
-        return t < 10 || t > 25 ? cal(s.substring(1)) : cal(s.substring(1)) + cal(s.substring(2));
+        return b;
     }
 }

lcof/面试题46. 把数字翻译成字符串/Solution.java

@@ -3,19 +3,17 @@
  * @return {number}
  */
 var translateNum = function (num) {
-    let res = 0;
-    num = num.toString();
-    function dfs(i) {
-        if (i >= num.length) {
-            res++;
-            return;
-        }
-        dfs(i + 1);
-        let tmp = +(num[i] + num[i + 1]);
-        if (num[i] !== '0' && tmp >= 0 && tmp < 26) {
-            dfs(i + 2);
+    const s = num.toString();
+    const n = s.length;
+    let a = 1;
+    let b = 1;
+    for (let i = 1; i < n; ++i) {
+        let c = b;
+        if (s[i - 1] === '1' || (s[i - 1] === '2' && s[i] < '6')) {
+            c += a;
         }
+        a = b;
+        b = c;
     }
-    dfs(0);
-    return res;
+    return b;
 };

lcof/面试题46. 把数字翻译成字符串/Solution.js

@@ -1,9 +1,11 @@
 class Solution:
     def translateNum(self, num: int) -> int:
-        def cal(s):
-            if len(s) < 2:
-                return 1
-            t = int(s[:2])
-            return cal(s[1:]) if t < 10 or t > 25 else cal(s[1:]) + cal(s[2:])
-
-        return cal(str(num))
+        s = str(num)
+        n = len(s)
+        a = b = 1
+        for i in range(1, n):
+            c = b
+            if s[i - 1] == "1" or (s[i - 1] == "2" and s[i] < "6"):
+                c += a
+            a, b = b, c
+        return b

lcof/面试题46. 把数字翻译成字符串/Solution.py

@@ -1,14 +1,15 @@
 function translateNum(num: number): number {
+    const s = num.toString();
+    const n = s.length;
     let a = 1;
     let b = 1;
-    const str = num + '';
-    for (let i = 1; i < str.length; i++) {
-        const val = Number(str[i - 1] + str[i]);
-        if (val >= 10 && val < 26) {
-            [a, b] = [b, a + b];
-        } else {
-            a = b;
+    for (let i = 1; i < n; ++i) {
+        let c = b;
+        if (s[i - 1] === '1' || (s[i - 1] === '2' && s[i] < '6')) {
+            c += a;
         }
+        a = b;
+        b = c;
     }
     return b;
 }