Sync LeetCode submission Runtime - 239 ms (72.40%), Memory - 385.4 MB (12.61%)

Author: koralkulacoglu

LeetCode/1087-longest-arithmetic-subsequence/README.md

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+<p>Given an array <code>nums</code> of integers, return <em>the length of the longest arithmetic subsequence in</em> <code>nums</code>.</p>
+
+<p><strong>Note</strong> that:</p>
+
+<ul>
+	<li>A <strong>subsequence</strong> is an array that can be derived from another array by deleting some or no elements without changing the order of the remaining elements.</li>
+	<li>A sequence <code>seq</code> is arithmetic if <code>seq[i + 1] - seq[i]</code> are all the same value (for <code>0 &lt;= i &lt; seq.length - 1</code>).</li>
+</ul>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [3,6,9,12]
+<strong>Output:</strong> 4
+<strong>Explanation: </strong> The whole array is an arithmetic sequence with steps of length = 3.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [9,4,7,2,10]
+<strong>Output:</strong> 3
+<strong>Explanation: </strong> The longest arithmetic subsequence is [4,7,10].
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [20,1,15,3,10,5,8]
+<strong>Output:</strong> 4
+<strong>Explanation: </strong> The longest arithmetic subsequence is [20,15,10,5].
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>2 &lt;= nums.length &lt;= 1000</code></li>
+	<li><code>0 &lt;= nums[i] &lt;= 500</code></li>
+</ul>

LeetCode/1087-longest-arithmetic-subsequence/solution.cpp

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+class Solution {
+public:
+    int longestArithSeqLength(vector<int>& nums) {
+        int n = nums.size();
+        int ans = 0;
+        for (int d=-500; d<=500; d++) {
+            vector<int> dp(2001, 0);
+            for (int num : nums) {
+                num += 500;
+                dp[num] = dp[num - d] + 1;
+                ans = max(ans, dp[num]);
+            }
+        }
+        return ans;
+    }
+};