Add solution for max k sum pairs

Author: kwnna15

two-pointer/k-sum-pairs/README.md

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+# 1679. Max Number of K-Sum Pairs
+
+## Description
+See https://leetcode.com/problems/max-number-of-k-sum-pairs/description/
+
+## Problem
+You are given an integer array `nums` and an integer `k`.
+
+In one operation, you can pick two numbers from the array whose sum equals `k` and remove them from the array.
+
+Return the maximum number of operations you can perform on the array.
+
+## Example 1
+
+```
+Input: nums = [1,2,3,4], k = 5
+Output: 2
+Explanation: Starting with nums = [1,2,3,4]:
+- Remove numbers 1 and 4, then nums = [2,3]
+- Remove numbers 2 and 3, then nums = []
+There are no more pairs that sum up to 5, hence a total of 2 operations.
+```
+
+## Example 2
+
+```
+Input: nums = [3,1,3,4,3], k = 6
+Output: 1
+Explanation: Starting with nums = [3,1,3,4,3]:
+- Remove the first two 3's, then nums = [1,4,3]
+There are no more pairs that sum up to 6, hence a total of 1 operation.
+```
+
+## Constraints
+
+```
+1 <= nums.length <= 105
+1 <= nums[i] <= 109
+1 <= k <= 109
+```

two-pointer/k-sum-pairs/ksumpairs.py

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+def max_operations(nums: list[int], k: int) -> int:
+    i = 0
+    j = len(nums) - 1
+    count = 0
+    nums.sort()
+    while j > i:
+        if nums[i] + nums[j] > k:
+            j = j - 1
+        elif nums[i] + nums[j] < k:
+            i = i + 1
+        else:
+            count = count + 1
+            nums[i] = nums[j] = 0
+            i = i + 1
+            j = j - 1
+    return count

two-pointer/k-sum-pairs/ksumpairs_test.py

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+from ksumpairs import max_operations
+
+def test_example_1():
+    nums = [1, 2, 3, 4]
+    k = 5
+    assert max_operations(nums, k) == 2
+
+def test_example_2():
+    nums = [3, 1, 3, 4, 3]
+    k = 6
+    assert max_operations(nums, k) == 1
+
+def test_example_3():
+    nums = [1, 2, 3, 4, 5, 6]
+    k = 7
+    assert max_operations(nums, k) == 3
+
+def test_example_4():
+    nums = [1, 1, 1, 1]
+    k = 2
+    assert max_operations(nums, k) == 2
+
+def test_example_5():
+    nums = [2, 2, 2, 2]
+    k = 4
+    assert max_operations(nums, k) == 2