+ problem 646

fruit-in · fruit-in · commit 25f98e182c34 · 2024-03-16T12:35:48.000+08:00
diff --git a/Problemset/0646-Maximum Length of Pair Chain/README.md b/Problemset/0646-Maximum Length of Pair Chain/README.md
@@ -0,0 +1,49 @@
+# 646. Maximum Length of Pair Chain
+You are given an array of `n` pairs `pairs` where <code>pairs[i] = [left<sub>i</sub>, right<sub>i</sub>]</code> and <code>left<sub>i</sub> < right<sub>i</sub></code>.
+
+A pair `p2 = [c, d]` **follows** a pair `p1 = [a, b]` if `b < c`. A **chain** of pairs can be formed in this fashion.
+
+Return *the length longest chain which can be formed*.
+
+You do not need to use up all the given intervals. You can select pairs in any order.
+
+#### Example 1:
+<pre>
+<strong>Input:</strong> pairs = [[1,2],[2,3],[3,4]]
+<strong>Output:</strong> 2
+<strong>Explanation:</strong> The longest chain is [1,2] -> [3,4].
+</pre>
+
+#### Example 2:
+<pre>
+<strong>Input:</strong> pairs = [[1,2],[7,8],[4,5]]
+<strong>Output:</strong> 3
+<strong>Explanation:</strong> The longest chain is [1,2] -> [4,5] -> [7,8].
+</pre>
+
+#### Constraints:
+* `n == pairs.length`
+* `1 <= n <= 1000`
+* <code>-1000 <= left<sub>i</sub> < right<sub>i</sub> <= 1000</code>
+
+## Solutions (Rust)
+
+### 1. Solution
+```Rust
+impl Solution {
+    pub fn find_longest_chain(mut pairs: Vec<Vec<i32>>) -> i32 {
+        pairs.sort_unstable_by_key(|p| (p[1], -p[0]));
+        let mut right = pairs[0][1];
+        let mut ret = 1;
+
+        for i in 1..pairs.len() {
+            if pairs[i][0] > right {
+                right = pairs[i][1];
+                ret += 1;
+            }
+        }
+
+        ret
+    }
+}
+```
diff --git a/Problemset/0646-Maximum Length of Pair Chain/README_CN.md b/Problemset/0646-Maximum Length of Pair Chain/README_CN.md
@@ -0,0 +1,49 @@
+# 646. 最长数对链
+给你一个由 `n` 个数对组成的数对数组 `pairs` ，其中 <code>pairs[i] = [left<sub>i</sub>, right<sub>i</sub>]</code> 且 <code>left<sub>i</sub> < right<sub>i</sub></code> 。
+
+现在，我们定义一种 **跟随** 关系，当且仅当 `b < c` 时，数对 `p2 = [c, d]` 才可以跟在 `p1 = [a, b]` 后面。我们用这种形式来构造 **数对链** 。
+
+找出并返回能够形成的 **最长数对链的长度** 。
+
+你不需要用到所有的数对，你可以以任何顺序选择其中的一些数对来构造。
+
+#### 示例 1:
+<pre>
+<strong>输入:</strong> pairs = [[1,2],[2,3],[3,4]]
+<strong>输出:</strong> 2
+<strong>解释:</strong> 最长的数对链是 [1,2] -> [3,4] 。
+</pre>
+
+#### 示例 2:
+<pre>
+<strong>输入:</strong> pairs = [[1,2],[7,8],[4,5]]
+<strong>输出:</strong> 3
+<strong>解释:</strong> 最长的数对链是 [1,2] -> [4,5] -> [7,8] 。
+</pre>
+
+#### 提示:
+* `n == pairs.length`
+* `1 <= n <= 1000`
+* <code>-1000 <= left<sub>i</sub> < right<sub>i</sub> <= 1000</code>
+
+## 题解 (Rust)
+
+### 1. 题解
+```Rust
+impl Solution {
+    pub fn find_longest_chain(mut pairs: Vec<Vec<i32>>) -> i32 {
+        pairs.sort_unstable_by_key(|p| (p[1], -p[0]));
+        let mut right = pairs[0][1];
+        let mut ret = 1;
+
+        for i in 1..pairs.len() {
+            if pairs[i][0] > right {
+                right = pairs[i][1];
+                ret += 1;
+            }
+        }
+
+        ret
+    }
+}
+```
diff --git a/Problemset/0646-Maximum Length of Pair Chain/Solution.rs b/Problemset/0646-Maximum Length of Pair Chain/Solution.rs
@@ -0,0 +1,16 @@
+impl Solution {
+    pub fn find_longest_chain(mut pairs: Vec<Vec<i32>>) -> i32 {
+        pairs.sort_unstable_by_key(|p| (p[1], -p[0]));
+        let mut right = pairs[0][1];
+        let mut ret = 1;
+
+        for i in 1..pairs.len() {
+            if pairs[i][0] > right {
+                right = pairs[i][1];
+                ret += 1;
+            }
+        }
+
+        ret
+    }
+}
diff --git a/README.md b/README.md
@@ -391,6 +391,7 @@
 [641][641l]  |[Design Circular Deque][641]                                                          |![rs]
 [643][643l]  |[Maximum Average Subarray I][643]                                                     |![rs]
 [645][645l]  |[Set Mismatch][645]                                                                   |![rs]
+[646][646l]  |[Maximum Length of Pair Chain][646]                                                   |![rs]
 [647][647l]  |[Palindromic Substrings][647]                                                         |![rb]
 [648][648l]  |[Replace Words][648]                                                                  |![py]
 [652][652l]  |[Find Duplicate Subtrees][652]                                                        |![py]
@@ -1791,6 +1792,7 @@
 [641]:Problemset/0641-Design%20Circular%20Deque/README.md#641-design-circular-deque
 [643]:Problemset/0643-Maximum%20Average%20Subarray%20I/README.md#643-maximum-average-subarray-i
 [645]:Problemset/0645-Set%20Mismatch/README.md#645-set-mismatch
+[646]:Problemset/0646-Maximum%20Length%20of%20Pair%20Chain/README.md#646-maximum-length-of-pair-chain
 [647]:Problemset/0647-Palindromic%20Substrings/README.md#647-palindromic-substrings
 [648]:Problemset/0648-Replace%20Words/README.md#648-replace-words
 [652]:Problemset/0652-Find%20Duplicate%20Subtrees/README.md#652-find-duplicate-subtrees
@@ -3189,6 +3191,7 @@
 [641l]:https://leetcode.com/problems/design-circular-deque/
 [643l]:https://leetcode.com/problems/maximum-average-subarray-i/
 [645l]:https://leetcode.com/problems/set-mismatch/
+[646l]:https://leetcode.com/problems/maximum-length-of-pair-chain/
 [647l]:https://leetcode.com/problems/palindromic-substrings/
 [648l]:https://leetcode.com/problems/replace-words/
 [652l]:https://leetcode.com/problems/find-duplicate-subtrees/
diff --git a/README_CN.md b/README_CN.md
@@ -391,6 +391,7 @@
 [641][641l]  |[设计循环双端队列][641]                                   |![rs]
 [643][643l]  |[子数组最大平均数 I][643]                                 |![rs]
 [645][645l]  |[错误的集合][645]                                         |![rs]
+[646][646l]  |[最长数对链][646]                                         |![rs]
 [647][647l]  |[回文子串][647]                                           |![rb]
 [648][648l]  |[单词替换][648]                                           |![py]
 [652][652l]  |[寻找重复的子树][652]                                     |![py]
@@ -1791,6 +1792,7 @@
 [641]:Problemset/0641-Design%20Circular%20Deque/README_CN.md#641-设计循环双端队列
 [643]:Problemset/0643-Maximum%20Average%20Subarray%20I/README_CN.md#643-子数组最大平均数-i
 [645]:Problemset/0645-Set%20Mismatch/README_CN.md#645-错误的集合
+[646]:Problemset/0646-Maximum%20Length%20of%20Pair%20Chain/README_CN.md#646-最长数对链
 [647]:Problemset/0647-Palindromic%20Substrings/README_CN.md#647-回文子串
 [648]:Problemset/0648-Replace%20Words/README_CN.md#648-单词替换
 [652]:Problemset/0652-Find%20Duplicate%20Subtrees/README_CN.md#652-寻找重复的子树
@@ -3189,6 +3191,7 @@
 [641l]:https://leetcode.cn/problems/design-circular-deque/
 [643l]:https://leetcode.cn/problems/maximum-average-subarray-i/
 [645l]:https://leetcode.cn/problems/set-mismatch/
+[646l]:https://leetcode.cn/problems/maximum-length-of-pair-chain/
 [647l]:https://leetcode.cn/problems/palindromic-substrings/
 [648l]:https://leetcode.cn/problems/replace-words/
 [652l]:https://leetcode.cn/problems/find-duplicate-subtrees/
