add links

Author: EndlessCheng

copypasta/fenwick_tree.go

@@ -106,6 +106,7 @@ func fenwickTree(n int) {
 
 	// 求逆序对的方法之一
 	// 如果 a 范围较大则需要离散化（但这样还不如直接用归并排序）
+	// 归并做法见 misc.go 中的 mergeCount
 	// 扩展 https://codeforces.com/problemset/problem/362/C
 	// 环形最小逆序对 https://www.luogu.com.cn/problem/solution/P2995
 	// 扩展：某些位置上的数待定时的逆序对的期望值 https://codeforces.com/problemset/problem/1096/F

copypasta/geometry.go

@@ -832,6 +832,7 @@ func vec2Collection() {
 	// https://algs4.cs.princeton.edu/code/edu/princeton/cs/algs4/GrahamScan.java.html
 	// NOTE: 坐标值范围不超过 M 的凸多边形的顶点数为 O(√M) 个
 	// 模板题 https://www.luogu.com.cn/problem/P2742 LC587 https://leetcode-cn.com/problems/erect-the-fence/
+	// 构造 LCP15 https://leetcode-cn.com/problems/you-le-yuan-de-mi-gong/
 	// 限制区间长度的区间最大均值问题 https://codeforces.com/edu/course/2/lesson/6/4/practice/contest/285069/problem/A
 	// todo poj 2187 1113 1912 3608 2079 3246 3689
 	convexHull := func(ps []vec) (q []vec) {

copypasta/misc.go

@@ -416,10 +416,11 @@ func mapPos(a, b []int) []int {
 	return ids
 }
 
-// 逆序对
+// 归并排序与逆序对
 // LC 面试题 51 https://leetcode-cn.com/problems/shu-zu-zhong-de-ni-xu-dui-lcof/
-// EXTRA: LC 327 https://leetcode-cn.com/problems/count-of-range-sum/
-//        LC 493 https://leetcode-cn.com/problems/reverse-pairs/
+// EXTRA: LC315 https://leetcode-cn.com/problems/count-of-smaller-numbers-after-self/
+//        LC327 https://leetcode-cn.com/problems/count-of-range-sum/
+//        LC493 https://leetcode-cn.com/problems/reverse-pairs/
 // 一张关于归并排序的好图 https://www.cnblogs.com/chengxiao/p/6194356.html
 func mergeCount(a []int) int64 {
 	n := len(a)

copypasta/sort.go

@@ -369,7 +369,12 @@ func sortCollections() {
 	//       https://codeforces.com/gym/101649 K
 	//       https://www.luogu.com.cn/problem/P1570
 	//       https://loj.ac/p/149
-	// 连续子段的算数平均值 https://codeforces.com/edu/course/2/lesson/6/4/practice/contest/285069/problem/A https://codeforces.com/problemset/problem/1003/C https://www.luogu.com.cn/problem/P1404 https://www.acwing.com/problem/content/104/
+	// 有长度限制的连续子段的（最大/最小）算数平均值
+	//     https://codeforces.com/edu/course/2/lesson/6/4/practice/contest/285069/problem/A
+	//     https://codeforces.com/problemset/problem/1003/C
+	//     https://www.luogu.com.cn/problem/P1404
+	//     https://www.acwing.com/problem/content/104/
+	//     LC644 https://leetcode-cn.com/problems/maximum-average-subarray-ii/
 	//     O(n) 做法见 04 年集训队周源论文《浅谈数形结合思想在信息学竞赛中的应用》（或紫书 p.243 例题 8-9，UVa 1451 https://onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=447&page=show_problem&problem=4197）
 	// 与 0-1 背包结合，即最优比率背包 https://www.luogu.com.cn/problem/P4377 https://ac.nowcoder.com/acm/contest/2271/F
 	// 与生成树结合，即最优比率生成树 https://www.luogu.com.cn/problem/P4951 http://poj.org/problem?id=2728