Create NumberOfPairs.cpp

Arrays/NumberOfPairs.cpp

@@ -0,0 +1,44 @@
+class Solution {
+  public:
+  int f(int val,vector<int>&brr){
+      int s=0,e=brr.size()-1,index=-1;
+      while(s<=e){
+          int mid=s+(e-s)/2;
+          if(brr[mid]<=val){
+              index=mid;
+              s=mid+1;
+          }
+          else{
+              e=mid-1;
+          }
+      }
+      return index;
+  }
+    long long countPairs(vector<int> &arr, vector<int> &brr) {
+        // Your Code goes here.
+        long long ans=0;
+        sort(brr.begin(),brr.end());
+        int one=0,two=0,threeFour=0;
+        int n=brr.size();
+        for(auto i:brr){
+            if(i==1){
+                one++;
+            }
+            else if(i==2)
+            two++;
+            else if(i==3 || i==4){
+                threeFour++;
+            }
+        }
+        for(auto i:arr){
+            if(i!=1){
+                ans+=one;
+                if(i==2) ans-=threeFour;
+                if(i==3) ans+=two;
+                int index=f(i,brr);
+                ans+=n-index-1;
+            }
+        }
+        return ans;
+    }
+};