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-rw-r--r--other/num_smaller_num_self.cpp44
1 files changed, 44 insertions, 0 deletions
diff --git a/other/num_smaller_num_self.cpp b/other/num_smaller_num_self.cpp
new file mode 100644
index 0000000..49b3ed3
--- /dev/null
+++ b/other/num_smaller_num_self.cpp
@@ -0,0 +1,44 @@
+#include "leetcode.h"
+
+class Solution {
+public:
+ vector<int> countSmaller(vector<int> &nums) {
+ int n = nums.size();
+ vector<pair<int, int>> vp(n);
+ vector<int> count(n, 0);
+ for (int i = 0; i < n; i++)
+ vp[i] = make_pair(nums[i], i);
+ sort(count, vp, 0, n - 1);
+ return count;
+ }
+
+private:
+ void merge(vector<int> &count, vector<pair<int, int>> &vp, int left, int mid,
+ int right) {
+ vector<pair<int, int>> tmp(right - left + 1);
+ int i = left, j = mid + 1, k = 0;
+ while (i <= mid && j <= right) {
+ if (vp[i].first <= vp[j].first)
+ tmp[k++] = vp[j++];
+ else {
+ count[vp[i].second] += right - j + 1;
+ tmp[k++] = vp[i++];
+ }
+ }
+ while (i <= mid)
+ tmp[k++] = vp[i++];
+ while (j <= right)
+ tmp[k++] = vp[j++];
+ for (int i = left; i <= right; i++)
+ vp[i] = tmp[i - left];
+ }
+ void sort(vector<int> &count, vector<pair<int, int>> &vp, int left,
+ int right) {
+ if (left >= right)
+ return;
+ int mid = left + (right - left) / 2;
+ sort(count, vp, left, mid);
+ sort(count, vp, mid + 1, right);
+ merge(count, vp, left, mid, right);
+ }
+};