feat: add solutions to lc problem: No.1781

No.1781.Sum of Beauty of All Substrings

Author: yanglbme

solution/0900-0999/0912.Sort an Array/README.md

@@ -42,9 +42,15 @@
 
 **方法一：快速排序**
 
+快速排序是一种高效的排序算法。它的基本思想是通过一趟排序将待排序的数据分割成独立的两部分，其中一部分的所有数据都比另外一部分的所有数据都要小，然后再按此方法对这两部分数据分别进行快速排序，整个排序过程可以递归进行，以此达到整个数据变成有序序列。
+
+时间复杂度 $O(n \times \log n)$，空间复杂度 $O(\log n)$。其中 $n$ 为数组长度。
+
 **方法二：归并排序**
 
-以上两种方法时间复杂度均为 O(nlogn)。
+归并排序是一种分治算法，其思想是将待排序的数据序列不断地折半拆分，直到每个数据块只有一个元素为止，然后再按照拆分的顺序将每个数据块两两合并，在合并的过程中进行排序，最终得到一个有序的数据序列。
+
+归并排序是一种稳定的排序算法，时间复杂度为 $O(n \times \log n)$，空间复杂度为 $O(n)$。其中 $n$ 为数组长度。
 
 <!-- tabs:start -->
 

solution/1700-1799/1781.Sum of Beauty of All Substrings/README.md

@@ -43,7 +43,11 @@
 
 <!-- 这里可写通用的实现逻辑 -->
 
-计数器实现。`s[i, j]` 的 counter 可用于计算 `s[i, j + 1]`。
+**方法一：枚举 + 计数**
+
+枚举每个子串的起点，找到以该起点为左端点的所有子串，然后计算每个子串的美丽值，最后将所有子串的美丽值相加即可。
+
+时间复杂度 O(n^2 \times C)，空间复杂度 $O(C)$。其中 $n$ 为字符串的长度，而 $C$ 为字符集的大小。本题中 $C = 26$。
 
 <!-- tabs:start -->
 
@@ -56,11 +60,10 @@ class Solution:
     def beautySum(self, s: str) -> int:
         ans, n = 0, len(s)
         for i in range(n):
-            counter = Counter()
+            cnt = Counter()
             for j in range(i, n):
-                counter[s[j]] += 1
-                t = [v for v in counter.values() if v]
-                ans += max(t) - min(t)
+                cnt[s[j]] += 1
+                ans += max(cnt.values()) - min(cnt.values())
         return ans
 ```
 
@@ -70,17 +73,15 @@ class Solution:
 
 ```java
 class Solution {
-
     public int beautySum(String s) {
         int ans = 0;
         int n = s.length();
         for (int i = 0; i < n; ++i) {
-            int[] counter = new int[26];
+            int[] cnt = new int[26];
             for (int j = i; j < n; ++j) {
-                ++counter[s.charAt(j) - 'a'];
-                int mi = 1000;
-                int mx = 0;
-                for (int v : counter) {
+                ++cnt[s.charAt(j) - 'a'];
+                int mi = 1000, mx = 0;
+                for (int v : cnt) {
                     if (v > 0) {
                         mi = Math.min(mi, v);
                         mx = Math.max(mx, v);
@@ -102,14 +103,14 @@ public:
     int beautySum(string s) {
         int ans = 0;
         int n = s.size();
+        int cnt[26];
         for (int i = 0; i < n; ++i) {
-            vector<int> counter(26);
+            memset(cnt, 0, sizeof cnt);
             for (int j = i; j < n; ++j) {
-                ++counter[s[j] - 'a'];
-                int mi = 1000;
-                int mx = 0;
-                for (int v : counter) {
-                    if (v) {
+                ++cnt[s[j] - 'a'];
+                int mi = 1000, mx = 0;
+                for (int& v : cnt) {
+                    if (v > 0) {
                         mi = min(mi, v);
                         mx = max(mx, v);
                     }
@@ -125,38 +126,48 @@ public:
 ### **Go**
 
 ```go
-func beautySum(s string) int {
-	ans, n := 0, len(s)
-	for i := 0; i < n; i++ {
-		counter := make([]int, 26)
-		for j := i; j < n; j++ {
-			counter[s[j]-'a']++
+func beautySum(s string) (ans int) {
+	for i := range s {
+		cnt := [26]int{}
+		for j := i; j < len(s); j++ {
+			cnt[s[j]-'a']++
 			mi, mx := 1000, 0
-			for _, v := range counter {
+			for _, v := range cnt {
 				if v > 0 {
-					mi = min(mi, v)
-					mx = max(mx, v)
+					if mi > v {
+						mi = v
+					}
+					if mx < v {
+						mx = v
+					}
 				}
 			}
 			ans += mx - mi
 		}
 	}
-	return ans
-}
-
-func max(a, b int) int {
-	if a > b {
-		return a
-	}
-	return b
+	return
 }
+```
 
-func min(a, b int) int {
-	if a < b {
-		return a
-	}
-	return b
-}
+### **JavaScript**
+
+```js
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var beautySum = function (s) {
+    let ans = 0;
+    for (let i = 0; i < s.length; ++i) {
+        const cnt = new Map();
+        for (let j = i; j < s.length; ++j) {
+            cnt.set(s[j], (cnt.get(s[j]) || 0) + 1);
+            const t = Array.from(cnt.values());
+            ans += Math.max(...t) - Math.min(...t);
+        }
+    }
+    return ans;
+};
 ```
 
 ### **...**

solution/1700-1799/1781.Sum of Beauty of All Substrings/README_EN.md

@@ -46,11 +46,10 @@ class Solution:
     def beautySum(self, s: str) -> int:
         ans, n = 0, len(s)
         for i in range(n):
-            counter = Counter()
+            cnt = Counter()
             for j in range(i, n):
-                counter[s[j]] += 1
-                t = [v for v in counter.values() if v]
-                ans += max(t) - min(t)
+                cnt[s[j]] += 1
+                ans += max(cnt.values()) - min(cnt.values())
         return ans
 ```
 
@@ -62,12 +61,11 @@ class Solution {
         int ans = 0;
         int n = s.length();
         for (int i = 0; i < n; ++i) {
-            int[] counter = new int[26];
+            int[] cnt = new int[26];
             for (int j = i; j < n; ++j) {
-                ++counter[s.charAt(j) - 'a'];
-                int mi = 1000;
-                int mx = 0;
-                for (int v : counter) {
+                ++cnt[s.charAt(j) - 'a'];
+                int mi = 1000, mx = 0;
+                for (int v : cnt) {
                     if (v > 0) {
                         mi = Math.min(mi, v);
                         mx = Math.max(mx, v);
@@ -89,14 +87,14 @@ public:
     int beautySum(string s) {
         int ans = 0;
         int n = s.size();
+        int cnt[26];
         for (int i = 0; i < n; ++i) {
-            vector<int> counter(26);
+            memset(cnt, 0, sizeof cnt);
             for (int j = i; j < n; ++j) {
-                ++counter[s[j] - 'a'];
-                int mi = 1000;
-                int mx = 0;
-                for (int v : counter) {
-                    if (v) {
+                ++cnt[s[j] - 'a'];
+                int mi = 1000, mx = 0;
+                for (int& v : cnt) {
+                    if (v > 0) {
                         mi = min(mi, v);
                         mx = max(mx, v);
                     }
@@ -112,38 +110,48 @@ public:
 ### **Go**
 
 ```go
-func beautySum(s string) int {
-	ans, n := 0, len(s)
-	for i := 0; i < n; i++ {
-		counter := make([]int, 26)
-		for j := i; j < n; j++ {
-			counter[s[j]-'a']++
+func beautySum(s string) (ans int) {
+	for i := range s {
+		cnt := [26]int{}
+		for j := i; j < len(s); j++ {
+			cnt[s[j]-'a']++
 			mi, mx := 1000, 0
-			for _, v := range counter {
+			for _, v := range cnt {
 				if v > 0 {
-					mi = min(mi, v)
-					mx = max(mx, v)
+					if mi > v {
+						mi = v
+					}
+					if mx < v {
+						mx = v
+					}
 				}
 			}
 			ans += mx - mi
 		}
 	}
-	return ans
-}
-
-func max(a, b int) int {
-	if a > b {
-		return a
-	}
-	return b
+	return
 }
+```
 
-func min(a, b int) int {
-	if a < b {
-		return a
-	}
-	return b
-}
+### **JavaScript**
+
+```js
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var beautySum = function (s) {
+    let ans = 0;
+    for (let i = 0; i < s.length; ++i) {
+        const cnt = new Map();
+        for (let j = i; j < s.length; ++j) {
+            cnt.set(s[j], (cnt.get(s[j]) || 0) + 1);
+            const t = Array.from(cnt.values());
+            ans += Math.max(...t) - Math.min(...t);
+        }
+    }
+    return ans;
+};
 ```
 
 ### **...**

solution/1700-1799/1781.Sum of Beauty of All Substrings/Solution.cpp

@@ -3,14 +3,14 @@ class Solution {
     int beautySum(string s) {
         int ans = 0;
         int n = s.size();
+        int cnt[26];
         for (int i = 0; i < n; ++i) {
-            vector<int> counter(26);
+            memset(cnt, 0, sizeof cnt);
             for (int j = i; j < n; ++j) {
-                ++counter[s[j] - 'a'];
-                int mi = 1000;
-                int mx = 0;
-                for (int v : counter) {
-                    if (v) {
+                ++cnt[s[j] - 'a'];
+                int mi = 1000, mx = 0;
+                for (int& v : cnt) {
+                    if (v > 0) {
                         mi = min(mi, v);
                         mx = max(mx, v);
                     }

solution/1700-1799/1781.Sum of Beauty of All Substrings/Solution.go

@@ -1,32 +1,21 @@
-func beautySum(s string) int {
-	ans, n := 0, len(s)
-	for i := 0; i < n; i++ {
-		counter := make([]int, 26)
-		for j := i; j < n; j++ {
-			counter[s[j]-'a']++
+func beautySum(s string) (ans int) {
+	for i := range s {
+		cnt := [26]int{}
+		for j := i; j < len(s); j++ {
+			cnt[s[j]-'a']++
 			mi, mx := 1000, 0
-			for _, v := range counter {
+			for _, v := range cnt {
 				if v > 0 {
-					mi = min(mi, v)
-					mx = max(mx, v)
+					if mi > v {
+						mi = v
+					}
+					if mx < v {
+						mx = v
+					}
 				}
 			}
 			ans += mx - mi
 		}
 	}
-	return ans
-}
-
-func max(a, b int) int {
-	if a > b {
-		return a
-	}
-	return b
-}
-
-func min(a, b int) int {
-	if a < b {
-		return a
-	}
-	return b
+	return
 }

solution/1700-1799/1781.Sum of Beauty of All Substrings/Solution.java

@@ -3,12 +3,11 @@ public int beautySum(String s) {
         int ans = 0;
         int n = s.length();
         for (int i = 0; i < n; ++i) {
-            int[] counter = new int[26];
+            int[] cnt = new int[26];
             for (int j = i; j < n; ++j) {
-                ++counter[s.charAt(j) - 'a'];
-                int mi = 1000;
-                int mx = 0;
-                for (int v : counter) {
+                ++cnt[s.charAt(j) - 'a'];
+                int mi = 1000, mx = 0;
+                for (int v : cnt) {
                     if (v > 0) {
                         mi = Math.min(mi, v);
                         mx = Math.max(mx, v);

solution/1700-1799/1781.Sum of Beauty of All Substrings/Solution.js

@@ -0,0 +1,16 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var beautySum = function (s) {
+    let ans = 0;
+    for (let i = 0; i < s.length; ++i) {
+        const cnt = new Map();
+        for (let j = i; j < s.length; ++j) {
+            cnt.set(s[j], (cnt.get(s[j]) || 0) + 1);
+            const t = Array.from(cnt.values());
+            ans += Math.max(...t) - Math.min(...t);
+        }
+    }
+    return ans;
+};

solution/1700-1799/1781.Sum of Beauty of All Substrings/Solution.py

@@ -2,9 +2,8 @@ class Solution:
     def beautySum(self, s: str) -> int:
         ans, n = 0, len(s)
         for i in range(n):
-            counter = Counter()
+            cnt = Counter()
             for j in range(i, n):
-                counter[s[j]] += 1
-                t = [v for v in counter.values() if v]
-                ans += max(t) - min(t)
+                cnt[s[j]] += 1
+                ans += max(cnt.values()) - min(cnt.values())
         return ans