Time: 128 ms (96.40%), Space: 76 MB (88.94%) - LeetHub

arpitkekri · Nov 12, 2021 · 8342b55 · 8342b55
1 parent ece3976
commit 8342b55
Showing 1 changed file with 31 additions and 0 deletions.
diff --git a/count-of-smaller-numbers-after-self/count-of-smaller-numbers-after-self.cpp b/count-of-smaller-numbers-after-self/count-of-smaller-numbers-after-self.cpp
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+class Solution {
+public:
+
+    void update(int idx, vector<int> &BIT) {
+        while(idx < BIT.size()) {
+            BIT[idx]++;
+            idx += idx & -idx;
+        }
+    }
+
+    int answer(int idx, vector<int> &BIT) {
+        int small = 0;
+        while(idx > 0) {
+            small += BIT[idx];
+            idx -= idx & -idx;
+        }
+        return small;
+    }
+
+    vector<int> countSmaller(vector<int>& nums) {
+        int n = nums.size();
+        vector<int> res(n, 0);
+        vector<int> BIT(20005, 0);
+
+        for(int i = n-1; i >= 0; i--) {
+            res[i] = answer(nums[i] + 10001 - 1, BIT);
+            update(nums[i] + 10001, BIT);
+        }
+        return res;
+    }
+};