随笔分类 - 树状数组
摘要：题意： 给出一个数组，元素有正有负有0，问其区间和小于 t 的子区间的个数。 sum[ r ]-sum[ l-1 ]<t，其中sum是a的前缀和。 实现的方法就是从前往后对于每一个sum[ i ]，看在它前面有多少个大于等于sum[ i ] - t 的前缀和。 树状数组维护的是 i 前面有几个数小于
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摘要：Every year, Farmer John's N (1 <= N <= 20,000) cows attend "MooFest",a social gathering of cows from around the world. MooFest involves a variety of e
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摘要：There is an apple tree outside of kaka's house. Every autumn, a lot of apples will grow in the tree. Kaka likes apple very much, so he has been carefu
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摘要：Farmer John's cows have discovered that the clover growing along the ridge of the hill (which we can think of as a one-dimensional number line) in his
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摘要：Suppose that the fourth generation mobile phone base stations in the Tampere area operate as follows. The area is divided into squares. The squares fo
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摘要：Astronomers often examine star maps where stars are represented by points on a plane and each star has Cartesian coordinates. Let the level of a star
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摘要：Japan plans to welcome the ACM ICPC World Finals and a lot of roads must be built for the venue. Japan is tall island with N cities on the East coast
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摘要：In this problem, you have to analyze a particular sorting algorithm. The algorithm processes a sequence of n distinct integers by swapping two adjacen
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摘要：题目是让每次对一个子矩阵进行翻转（0变1,1变0）， 然后有多次询问，询问某个点是0还是1 这题可以用二维的树状数组来解决，考虑传统的树状数组是改变某个点，然后查询某一段， 而这个题是改变某一段，查询某个点，需要进行一下转换，将原来的改值变成查询， 查询变成改值。改制时相当于对区间分别进行修改，而查
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