线段树

来源：互联网发布：《和阅读》软件编辑：程序博客网时间：2024/05/18 09:18

先看下线段树的介绍，下面这个链接讲得还不错 http://hi.baidu.com/semluhiigubbqvq/item/be736a33a8864789f4e4ad18

本文所讲的线段树和该文有微小区别，在该文中节点[0, 7]的左儿子为[0,3]，右儿子为[4,7]，不包含mid，而我们的线段树是包含的，即昨儿子为[0,3]，右儿子为[3,7]。

现在我们用线段树解决以下问题（小米笔试题）：

给定n个线段，每个线段告诉起点和终点，求线段总长度和，重合的部分只算一次。例如[0,3]，[2,5]，线段长度总和为[0,5]为5。实现代码如下：

#include <iostream>using namespace std;struct node{    int left;    int right;    int cover;    node()    {        cover = 0;    }};class LineSegmentTree{    private:    node *tree;    public:    LineSegmentTree() {};    LineSegmentTree(int left, int right);    ~LineSegmentTree();    void init(int left, int right, int root);    void insert(int left, int right, int root=1);    int sum(int root=1);};LineSegmentTree:: LineSegmentTree(int left, int right){    tree = new node[(right-left)*3]();    init(left, right, 1);}void LineSegmentTree:: init(int left, int right, int root){    tree[root].left = left;    tree[root].right = right;    if(right - left == 1)    {        return;    }    int mid = (left + right) / 2;    init(left, mid, 2*root);    init(mid, right, 2*root+1);}void LineSegmentTree:: insert(int left, int right, int root){    if(right <= left)    {        return;    }    if(left == tree[root].left && right == tree[root].right)    {        tree[root].cover++;        return;    }    int mid = (tree[root].right + tree[root].left) / 2;    if(mid >= right)    {        insert(left, right, 2*root);    }    else if(mid <= left)    {        insert(left, right, 2*root+1);    }    else    {        insert(left, mid, 2*root);        insert(mid, right, 2*root+1);    }}int LineSegmentTree:: sum(int root){    if(tree[root].cover >= 1)    {        return tree[root].right - tree[root].left;    }    else if(tree[root].right - tree[root].left == 1)    {        return 0;    }    else    {        return sum(2*root) + sum(2*root+1);    }}LineSegmentTree:: ~LineSegmentTree(){    delete[] tree;}int main(){    LineSegmentTree t(1, 15);    t.insert(1, 4);    t.insert(3, 5);    t.insert(2, 6);    t.insert(3, 5);    t.insert(2, 3);    t.insert(12, 13);    t.insert(8, 13);    cout<<t.sum()<<endl;    return 0;}