Create 2040. Kth Smallest Product of Two Sorted Arrays

2040. Kth Smallest Product of Two Sorted Arrays

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+class Solution {
+public:
+    long long kthSmallestProduct(vector<int>& nums1, vector<int>& nums2, long long k) {
+        long long left = -1e10, right = 1e10;
+        while (left < right) {
+            long long mid = left + (right - left) / 2;
+            if (countProducts(nums1, nums2, mid) < k)
+                left = mid + 1;
+            else
+                right = mid;
+        }
+        return left;
+    }
+
+    long long countProducts(vector<int>& nums1, vector<int>& nums2, long long target) {
+        long long count = 0;
+        for (int num1 : nums1) {
+            if (num1 == 0) {
+                if (target >= 0) count += nums2.size();
+                continue;
+            }
+            int low = 0, high = nums2.size();
+            if (num1 > 0) {
+                while (low < high) {
+                    int mid = low + (high - low) / 2;
+                    if (1LL * num1 * nums2[mid] <= target)
+                        low = mid + 1;
+                    else
+                        high = mid;
+                }
+                count += low;
+            } else {
+                while (low < high) {
+                    int mid = low + (high - low) / 2;
+                    if (1LL * num1 * nums2[mid] <= target)
+                        high = mid;
+                    else
+                        low = mid + 1;
+                }
+                count += nums2.size() - low;
+            }
+        }
+        return count;
+    }
+};