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Consider a positive integer N written in standard notation with k+1 digits ai as ak ⋯a1a0 with 0≤ai 0. Then N is palindromic if and only if ai =ak− 阅读全文
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There is a kind of balanced binary search tree named red black tree in the data structure. It has the following 5 properties: (1) Every node is either 阅读全文
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A vertex cover of a graph is a set of vertices such that each edge of the graph is incident to at least one vertex of the set. Now given a graph with 阅读全文
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Given a singly linked list, you are supposed to rearrange its elements so that all the negative values appear before all of the non negatives, and all 阅读全文
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Cutting an integer means to cut a K digits lone integer Z into two integers of (K/2) digits long integers A and B. For example, after cutting Z = 1673 阅读全文
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In the big cities, the subway systems always look so complex to the visitors. To give you some sense, the following figure shows the map of Beijing su 阅读全文
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Given a syntax tree (binary), you are supposed to output the corresponding infix expression, with parentheses reflecting the precedences of the operat 阅读全文
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Recommendation system predicts the preference that a user would give to an item. Now you are asked to program a very simple recommendation system that 阅读全文
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The "eight queens puzzle" is the problem of placing eight chess queens on an 8×8 chessboard so that no two queens threaten each other. Thus, a solutio 阅读全文
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Suppose that all the keys in a binary tree are distinct positive integers. A unique binary tree can be determined by a given pair of postorder and ino 阅读全文
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In graph theory, an Eulerian path is a path in a graph which visits every edge exactly once. Similarly, an Eulerian circuit is an Eulerian path which 阅读全文
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Given some segments of rope, you are supposed to chain them into one rope. Each time you may only fold two segments into loops and chain them into one 阅读全文
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John got a full mark on PAT. He was so happy that he decided to hold a raffle（抽奖） for his followers on Weibo that is, he would select winners from eve 阅读全文
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An AVL tree is a self balancing binary search tree. In an AVL tree, the heights of the two child subtrees of any node differ by at most one; if at any 阅读全文
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The "Hamilton cycle problem" is to find a simple cycle that contains every vertex in a graph. Such a cycle is called a "Hamiltonian cycle". In this pr 阅读全文