[LeetCode Sync] Runtime - 65 ms (84.83%), Memory - 38.8 MB (83.18%)

Author: NamVr

2448-count-number-of-bad-pairs/README.md

@@ -0,0 +1,33 @@
+<p>You are given a <strong>0-indexed</strong> integer array <code>nums</code>. A pair of indices <code>(i, j)</code> is a <strong>bad pair</strong> if <code>i &lt; j</code> and <code>j - i != nums[j] - nums[i]</code>.</p>
+
+<p>Return<em> the total number of <strong>bad pairs</strong> in </em><code>nums</code>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [4,1,3,3]
+<strong>Output:</strong> 5
+<strong>Explanation:</strong> The pair (0, 1) is a bad pair since 1 - 0 != 1 - 4.
+The pair (0, 2) is a bad pair since 2 - 0 != 3 - 4, 2 != -1.
+The pair (0, 3) is a bad pair since 3 - 0 != 3 - 4, 3 != -1.
+The pair (1, 2) is a bad pair since 2 - 1 != 3 - 1, 1 != 2.
+The pair (2, 3) is a bad pair since 3 - 2 != 3 - 3, 1 != 0.
+There are a total of 5 bad pairs, so we return 5.
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<pre>
+<strong>Input:</strong> nums = [1,2,3,4,5]
+<strong>Output:</strong> 0
+<strong>Explanation:</strong> There are no bad pairs.
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>1 &lt;= nums[i] &lt;= 10<sup>9</sup></code></li>
+</ul>

2448-count-number-of-bad-pairs/solution.py

@@ -0,0 +1,16 @@
+class Solution:
+    def countBadPairs(self, nums: List[int]) -> int:
+        res = 0
+        cnt = {} # hashmap
+
+        for i in range(len(nums)):
+            # i - nums[i] is the intuition
+            diff = i - nums[i]
+
+            # count previous positions with same difference
+            c = cnt.get(diff, 0)
+
+            res += i - c
+            cnt[diff] = c + 1
+            
+        return res