Create count-pairs-in-two-arrays.cpp

Author: kamyu104

C++/count-pairs-in-two-arrays.cpp

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+// Time:  O(nlogn)
+// Space: O(1)
+
+class Solution {
+public:
+    long long countPairs(vector<int>& nums1, vector<int>& nums2) {
+        for (int i = 0; i < size(nums1); ++i) {
+            nums1[i] -= nums2[i];
+        }
+        sort(begin(nums1), end(nums1));
+        long long result = 0;
+        int left = 0, right = size(nums1) - 1;
+        while (left < right) {
+            if (nums1[left] > 0 || -nums1[left] < nums1[right]) {
+                result += right - left;
+                --right;
+            } else {
+                ++left;
+            }
+        }
+        return result;
+    }
+};