Create 1498.Number-of-Subsequences-That-Satisfy-the-Given-Sum-Conditi…

…on.cpp

Two_Pointers/1498.Number-of-Subsequences-That-Satisfy-the-Given-Sum-Condition/1498.Number-of-Subsequences-That-Satisfy-the-Given-Sum-Condition.cpp

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+class Solution {
+public:
+    int numSubseq(vector<int>& nums, int target) 
+    {
+        sort(nums.begin(), nums.end());
+        int n = nums.size();
+        long M = 1e9+7;
+        long ret = 0;
+        vector<long>power(n+1);
+            power[0] = 1;
+        for (int i=1; i<=n; i++)
+            power[i] = power[i-1] * 2 % M;
+
+        int j = n-1;    
+        for (int i=0; i<n; i++)
+        {            
+            while (j>=0 && nums[i]+nums[j] > target)
+                j--;
+            if (j<i) break;                        
+            ret = (ret + power[j-i]) % M;
+        }
+        return ret;
+    }
+};