feat: add solutions to lc problem: No.3403

yanglbme · yanglbme · commit da11fe0e356f · 2025-05-26T20:36:50.000+08:00
No.3403.Find the Lexicographically Largest String From the Box I
diff --git a/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/README.md b/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/README.md
@@ -79,7 +79,13 @@ tags:
 
 <!-- solution:start -->
 
-### 方法一
+### 方法一：枚举子串左端点
+
+如果我们固定子字符串的左端点，那么子字符串越长，字典序越大。假设子字符串左端点为 $i$，剩余子字符串的最小长度为 $\text{numFriends} - 1$，那么子字符串的右端点可以取到 $\min(n, i + n - (\text{numFriends} - 1))$，其中 $n$ 为字符串的长度。注意我们说的是左开右闭。
+
+我们枚举所有可能的左端点，取出对应的子字符串，比较字典序，最终得到字典序最大的子字符串。
+
+时间复杂度 $O(n^2)$，空间复杂度 $O(n)$。其中 $n$ 为字符串的长度。
 
 <!-- tabs:start -->
 
@@ -91,11 +97,7 @@ class Solution:
         if numFriends == 1:
             return word
         n = len(word)
-        ans = ""
-        for i in range(n):
-            k = min(n - i, n - numFriends + 1)
-            ans = max(ans, word[i : i + k])
-        return ans
+        return max(word[i : i + n - (numFriends - 1)] for i in range(n))
 ```
 
 #### Java
@@ -109,8 +111,7 @@ class Solution {
         int n = word.length();
         String ans = "";
         for (int i = 0; i < n; ++i) {
-            int k = Math.min(n - i, n - numFriends + 1);
-            String t = word.substring(i, i + k);
+            String t = word.substring(i, Math.min(n, i + n - (numFriends - 1)));
             if (ans.compareTo(t) < 0) {
                 ans = t;
             }
@@ -129,12 +130,13 @@ public:
         if (numFriends == 1) {
             return word;
         }
-        int n = word.size();
-        string ans;
+        int n = word.length();
+        string ans = "";
         for (int i = 0; i < n; ++i) {
-            int k = min(n - i, n - numFriends + 1);
-            string t = word.substr(i, k);
-            ans = max(ans, t);
+            string t = word.substr(i, min(n - i, n - (numFriends - 1)));
+            if (ans < t) {
+                ans = t;
+            }
         }
         return ans;
     }
@@ -149,9 +151,8 @@ func answerString(word string, numFriends int) (ans string) {
 		return word
 	}
 	n := len(word)
-	for i := range word {
-		k := min(n-i, n-numFriends+1)
-		t := word[i : i+k]
+	for i := 0; i < n; i++ {
+		t := word[i:min(n, i+n-(numFriends-1))]
 		ans = max(ans, t)
 	}
 	return
@@ -165,14 +166,11 @@ function answerString(word: string, numFriends: number): string {
     if (numFriends === 1) {
         return word;
     }
-    let ans: string = '';
     const n = word.length;
-    for (let i = 0; i < n; ++i) {
-        const k = Math.min(n - i, n - numFriends + 1);
-        const t = word.slice(i, i + k);
-        if (ans < t) {
-            ans = t;
-        }
+    let ans = '';
+    for (let i = 0; i < n; i++) {
+        const t = word.slice(i, Math.min(n, i + n - (numFriends - 1)));
+        ans = t > ans ? t : ans;
     }
     return ans;
 }
diff --git a/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/README_EN.md b/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/README_EN.md
@@ -77,7 +77,13 @@ tags:
 
 <!-- solution:start -->
 
-### Solution 1
+### Solution 1: Enumerate Substring Left Endpoints
+
+If we fix the left endpoint of the substring, the longer the substring, the larger its lexicographical order. Suppose the left endpoint of the substring is $i$, and the minimum length of the remaining substrings is $\text{numFriends} - 1$, then the right endpoint of the substring can be up to $\min(n, i + n - (\text{numFriends} - 1))$, where $n$ is the length of the string. Note that we are talking about left-closed, right-open intervals.
+
+We enumerate all possible left endpoints, extract the corresponding substrings, compare their lexicographical order, and finally obtain the lexicographically largest substring.
+
+The time complexity is $O(n^2)$, and the space complexity is $O(n)$, where $n$ is the length of the string.
 
 <!-- tabs:start -->
 
@@ -89,11 +95,7 @@ class Solution:
         if numFriends == 1:
             return word
         n = len(word)
-        ans = ""
-        for i in range(n):
-            k = min(n - i, n - numFriends + 1)
-            ans = max(ans, word[i : i + k])
-        return ans
+        return max(word[i : i + n - (numFriends - 1)] for i in range(n))
 ```
 
 #### Java
@@ -107,8 +109,7 @@ class Solution {
         int n = word.length();
         String ans = "";
         for (int i = 0; i < n; ++i) {
-            int k = Math.min(n - i, n - numFriends + 1);
-            String t = word.substring(i, i + k);
+            String t = word.substring(i, Math.min(n, i + n - (numFriends - 1)));
             if (ans.compareTo(t) < 0) {
                 ans = t;
             }
@@ -127,12 +128,13 @@ public:
         if (numFriends == 1) {
             return word;
         }
-        int n = word.size();
-        string ans;
+        int n = word.length();
+        string ans = "";
         for (int i = 0; i < n; ++i) {
-            int k = min(n - i, n - numFriends + 1);
-            string t = word.substr(i, k);
-            ans = max(ans, t);
+            string t = word.substr(i, min(n - i, n - (numFriends - 1)));
+            if (ans < t) {
+                ans = t;
+            }
         }
         return ans;
     }
@@ -147,9 +149,8 @@ func answerString(word string, numFriends int) (ans string) {
 		return word
 	}
 	n := len(word)
-	for i := range word {
-		k := min(n-i, n-numFriends+1)
-		t := word[i : i+k]
+	for i := 0; i < n; i++ {
+		t := word[i:min(n, i+n-(numFriends-1))]
 		ans = max(ans, t)
 	}
 	return
@@ -163,14 +164,11 @@ function answerString(word: string, numFriends: number): string {
     if (numFriends === 1) {
         return word;
     }
-    let ans: string = '';
     const n = word.length;
-    for (let i = 0; i < n; ++i) {
-        const k = Math.min(n - i, n - numFriends + 1);
-        const t = word.slice(i, i + k);
-        if (ans < t) {
-            ans = t;
-        }
+    let ans = '';
+    for (let i = 0; i < n; i++) {
+        const t = word.slice(i, Math.min(n, i + n - (numFriends - 1)));
+        ans = t > ans ? t : ans;
     }
     return ans;
 }
diff --git a/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.cpp b/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.cpp
@@ -4,12 +4,13 @@ class Solution {
         if (numFriends == 1) {
             return word;
         }
-        int n = word.size();
-        string ans;
+        int n = word.length();
+        string ans = "";
         for (int i = 0; i < n; ++i) {
-            int k = min(n - i, n - numFriends + 1);
-            string t = word.substr(i, k);
-            ans = max(ans, t);
+            string t = word.substr(i, min(n - i, n - (numFriends - 1)));
+            if (ans < t) {
+                ans = t;
+            }
         }
         return ans;
     }
diff --git a/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.go b/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.go
@@ -3,10 +3,9 @@ func answerString(word string, numFriends int) (ans string) {
 		return word
 	}
 	n := len(word)
-	for i := range word {
-		k := min(n-i, n-numFriends+1)
-		t := word[i : i+k]
+	for i := 0; i < n; i++ {
+		t := word[i:min(n, i+n-(numFriends-1))]
 		ans = max(ans, t)
 	}
 	return
-}
+}
diff --git a/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.java b/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.java
@@ -6,12 +6,11 @@ public String answerString(String word, int numFriends) {
         int n = word.length();
         String ans = "";
         for (int i = 0; i < n; ++i) {
-            int k = Math.min(n - i, n - numFriends + 1);
-            String t = word.substring(i, i + k);
+            String t = word.substring(i, Math.min(n, i + n - (numFriends - 1)));
             if (ans.compareTo(t) < 0) {
                 ans = t;
             }
         }
         return ans;
     }
-}
+}
diff --git a/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.py b/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.py
@@ -3,8 +3,4 @@ def answerString(self, word: str, numFriends: int) -> str:
         if numFriends == 1:
             return word
         n = len(word)
-        ans = ""
-        for i in range(n):
-            k = min(n - i, n - numFriends + 1)
-            ans = max(ans, word[i : i + k])
-        return ans
+        return max(word[i : i + n - (numFriends - 1)] for i in range(n))
diff --git a/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.ts b/solution/3400-3499/3403.Find the Lexicographically Largest String From the Box I/Solution.ts
@@ -2,14 +2,11 @@ function answerString(word: string, numFriends: number): string {
     if (numFriends === 1) {
         return word;
     }
-    let ans: string = '';
     const n = word.length;
-    for (let i = 0; i < n; ++i) {
-        const k = Math.min(n - i, n - numFriends + 1);
-        const t = word.slice(i, i + k);
-        if (ans < t) {
-            ans = t;
-        }
+    let ans = '';
+    for (let i = 0; i < n; i++) {
+        const t = word.slice(i, Math.min(n, i + n - (numFriends - 1)));
+        ans = t > ans ? t : ans;
     }
     return ans;
 }

Original file line number	Diff line number	Diff line change
`@@ -4,12 +4,13 @@ class Solution {`
`4`	`4`	`if (numFriends == 1) {`
`5`	`5`	`return word;`
`6`	`6`	`}`
`7`		`- int n = word.size();`
`8`		`- string ans;`
	`7`	`+ int n = word.length();`
	`8`	`+ string ans = "";`
`9`	`9`	`for (int i = 0; i < n; ++i) {`
`10`		`- int k = min(n - i, n - numFriends + 1);`
`11`		`- string t = word.substr(i, k);`
`12`		`- ans = max(ans, t);`
	`10`	`+ string t = word.substr(i, min(n - i, n - (numFriends - 1)));`
	`11`	`+ if (ans < t) {`
	`12`	`+ ans = t;`
	`13`	`+ }`
`13`	`14`	`}`
`14`	`15`	`return ans;`
`15`	`16`	`}`
Original file line number	Diff line number	Diff line change
`@@ -3,10 +3,9 @@ func answerString(word string, numFriends int) (ans string) {`
`3`	`3`	`return word`
`4`	`4`	`}`
`5`	`5`	`n := len(word)`
`6`		`- for i := range word {`
`7`		`- k := min(n-i, n-numFriends+1)`
`8`		`- t := word[i : i+k]`
	`6`	`+ for i := 0; i < n; i++ {`
	`7`	`+ t := word[i:min(n, i+n-(numFriends-1))]`
`9`	`8`	`ans = max(ans, t)`
`10`	`9`	`}`
`11`	`10`	`return`
`12`		`-}`
	`11`	`+}`
Original file line number	Diff line number	Diff line change
`@@ -6,12 +6,11 @@ public String answerString(String word, int numFriends) {`
`6`	`6`	`int n = word.length();`
`7`	`7`	`String ans = "";`
`8`	`8`	`for (int i = 0; i < n; ++i) {`
`9`		`- int k = Math.min(n - i, n - numFriends + 1);`
`10`		`- String t = word.substring(i, i + k);`
	`9`	`+ String t = word.substring(i, Math.min(n, i + n - (numFriends - 1)));`
`11`	`10`	`if (ans.compareTo(t) < 0) {`
`12`	`11`	`ans = t;`
`13`	`12`	`}`
`14`	`13`	`}`
`15`	`14`	`return ans;`
`16`	`15`	`}`
`17`		`-}`
	`16`	`+}`
Original file line number	Diff line number	Diff line change
`@@ -2,14 +2,11 @@ function answerString(word: string, numFriends: number): string {`
`2`	`2`	`if (numFriends === 1) {`
`3`	`3`	`return word;`
`4`	`4`	`}`
`5`		`- let ans: string = '';`
`6`	`5`	`const n = word.length;`
`7`		`- for (let i = 0; i < n; ++i) {`
`8`		`- const k = Math.min(n - i, n - numFriends + 1);`
`9`		`- const t = word.slice(i, i + k);`
`10`		`- if (ans < t) {`
`11`		`- ans = t;`
`12`		`- }`
	`6`	`+ let ans = '';`
	`7`	`+ for (let i = 0; i < n; i++) {`
	`8`	`+ const t = word.slice(i, Math.min(n, i + n - (numFriends - 1)));`
	`9`	`+ ans = t > ans ? t : ans;`
`13`	`10`	`}`
`14`	`11`	`return ans;`
`15`	`12`	`}`