Merge pull request #452 from Apoorv012/day7/q1

Day 7 Q 1

Author: zonedoutdg

Problems/Binary-Search/Day-07/sol/Apoorv012/Solution1.cpp

@@ -0,0 +1,51 @@
+/*
+Submission Link: https://codeforces.com/contest/1538/submission/356110702
+
+Instead of finding the pairs to be greater than equal to L, and less than equal to R
+I found the pairs that were less than equal to R separately, and less than L separately.
+and the answer was the difference of it.
+
+*/
+
+#include <bits/stdc++.h>
+using namespace std;
+
+int main() {
+    int t;
+    cin >> t;
+    while (t--) {
+        long long n, L, R;
+        cin >> n >> L >> R;
+        vector<long long> v(n);
+        for (auto &x: v) cin >> x;
+        sort(v.begin(), v.end());
+        long long lteR = 0, ltL = 0;
+        
+        long long l = 0, r = n-1;
+        while (l < r) {
+            long long s = v[l] + v[r];
+            // 1 2 3 4 5 ; 3-5
+            if (s <= R) {
+                lteR += r-l;
+                l++;
+            }
+            else {
+                r--;
+            }
+        }
+        l = 0, r = n-1;
+        while (l < r) {
+            long long s = v[l] + v[r];
+            // 1 2 3 4 5 ; 3-5
+            if (s < L) {
+                ltL += r-l;
+                l++;
+            }
+            else {
+                r--;
+            }
+        }
+        cout << (lteR - ltL) << endl;
+        // cout << lteR << " " << ltL << " " << (lteR - ltL) << endl;
+    }
+}