1711. Count Good Meals

Author: tridibsamanta

CountGoodMeals_1711.cpp

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+/*
+~ Author    : https://leetcode.com/tridib_2003/
+~ Problem   : 1711. Count Good Meals
+~ Link      : https://leetcode.com/problems/count-good-meals/
+*/
+
+class Solution {
+public:
+    #define MOD 1000000007
+
+    int countPairs(vector<int>& deliciousness) {
+
+        unordered_map<int, int> freq;
+
+        int ans = 0;
+
+        for (int i : deliciousness) {
+
+            for (int pw = 1; pw <= (1 << 22); pw *= 2) {
+
+                if (freq[pw - i])
+                    ans = (ans + freq[pw - i]) % MOD;
+            }
+
+            ++freq[i];
+        }
+
+        return ans;
+    }
+};