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看了网上的一些介绍线段树的文档,不得要领,有没有大侠推荐下适合初学者的?找给定数组的任意长度子数组的最大值(Priority)
用赢者树的结构实现
也能过,就是慢点
详细见下:
/*
Title : RMQ(Range Minimum Query)问题的Binary Tree解法,
查询一指定数列任意一段区间内最(大)元素的位置
Time Complex : O(n) 预处理, O(logn) 每次查询
Space Complex : O(3*n) Total space
Author : song
Date : 9.3.2005
*/
#include <cstdio>
const int MAX = 1<<16; //MAX is a power of 2 and just bigger than n
int key[MAX]; //数列
int n; //数列长度
int pp[MAX*2]; //binary tree数组,pp[i]保存i子树覆盖的区间里最值的序号
inline bool RMQcmp(int i, int j) //比较函数
{
//like a heap, here we us > to get a Minimum Result,
//and < to get a Maximum one
return key[i] > key[j];
}
void RMQCreate() //预处理,建树
{
int f = MAX, t = MAX + n - 1, i;
for(i = 0; i < n; ++i)
pp[i+MAX] = i;
for( ;f < t; f /= 2, t /= 2)
{
for(i = f; i < t ; i+= 2)
{
if( !RMQcmp(pp[i], pp[i+1]) )
pp[i/2] = pp[i];
else pp[i/2] = pp[i+1];
}
if(!(t&1)) pp[t/2] = pp[t];
}
}
int RMQFind(int ss, int ee) //返回原数列key[ss - ee]之间最小元素的序号
{
int k, f, t;
ss += MAX, ee += MAX;
k = !RMQcmp(pp[ss] ,pp[ee]) ? pp[ss] : pp[ee];
for( f = ss, t = ee; f < t; f/=2, t/=2)
{
if( !(f&1) && f + 1 < t && !RMQcmp(pp[f+1], k))
k = pp[f+1];
if( (t&1) && t - 1 > f && !RMQcmp(pp[t-1], k))
k = pp[t-1];
}
return k;
}
int main()
{
/*
main()里做的事:
1.先初始化好key数列,及比较函数RMQcmp()。key[]的名字可改,只要cmp对应上就行。
2.调用RMQCreate()预处理
3.查询key[0,n-1]之间最小元素的序号,只需调用RMQFind(0, n-1)
*/
return 0;
}
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