Create number-of-subsequences-that-satisfy-the-given-sum-condition.cpp

Author: kamyu104

C++/number-of-subsequences-that-satisfy-the-given-sum-condition.cpp

@@ -0,0 +1,35 @@
+// Time:  O(nlogn)
+// Space: O(n)
+
+class Solution {
+public:
+    int numSubseq(vector<int>& nums, int target) {
+        static const int MOD = 1e9 + 7;
+        sort(begin(nums), end(nums));
+        int result = 0;
+        int left = 0, right = nums.size() - 1;
+        while (left <= right) {
+            if (nums[left] + nums[right] > target) {
+                --right;
+            } else {
+                result = (result + pow(2, right - left, MOD)) % MOD;
+                ++left;
+            }
+        }
+        return result;
+    }
+
+private:
+    uint64_t pow(uint64_t a,uint64_t b, uint64_t m) {
+        a %= m;
+        uint64_t result = 1;
+        while (b) {
+            if (b & 1) {
+                result = (result * a) % m;
+            }
+            a = (a * a) % m;
+            b >>= 1;
+        }
+        return result;
+    }
+};