Create 1577.Number-of-Ways-Where-Square-of-Number-Is-Equal-to-Product…

…-of-Two-Numbers_v1.cpp

Two_Pointers/1577.Number-of-Ways-Where-Square-of-Number-Is-Equal-to-Product-of-Two-Numbers/1577.Number-of-Ways-Where-Square-of-Number-Is-Equal-to-Product-of-Two-Numbers_v1.cpp

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+class Solution {
+public:
+    int numTriplets(vector<int>& nums1, vector<int>& nums2) 
+    {
+        int ret = 0;
+        sort(nums1.begin(), nums1.end());
+        sort(nums2.begin(), nums2.end());
+        ret += helper(nums1,nums2);
+        ret += helper(nums2,nums1);
+        return ret;        
+    }
+
+    int helper(vector<int>& nums1, vector<int>& nums2)
+    {
+        int ret = 0;
+        int n = nums2.size();
+        for (long x: nums1)
+        {
+            int i = 0, j = n-1;
+            while (i<j)
+            {                
+                if (x*x==(long)nums2[i]*(long)nums2[j])
+                {
+                    if (nums2[i]==nums2[j])
+                    {
+                        int t = j-i+1;
+                        ret += t*(t-1)/2;
+                        break;
+                    }
+                    else
+                    {
+                        int i0 = i; int j0=j;
+                        while (i+1<n && nums2[i+1]==nums2[i])
+                            i++;
+                        while (j-1<n && nums2[j-1]==nums2[j])
+                            j--;
+                        ret += abs(i-i0+1)*abs(j0-j+1);
+                        i++;
+                        j--;                        
+                    }
+                }                    
+                else if (x*x<(long)nums2[i]*(long)nums2[j])
+                    j--;
+                else
+                    i++;
+            }
+        }
+        return ret;
+    }
+};