POJ2418/openjudge Hardwood species 二叉搜索树

描述

Hardwoods are the botanical group of trees that have broad leaves, produce a fruit or nut, and generally go dormant in the winter. 
America's temperate climates produce forests with hundreds of hardwood species -- trees that share certain biological characteristics. Although oak, maple and cherry all are types of hardwood trees, for example, they are different species. Together, all the hardwood species represent 40 percent of the trees in the United States. 

On the other hand, softwoods, or conifers, from the Latin word meaning "cone-bearing," have needles. Widely available US softwoods include cedar, fir, hemlock, pine, redwood, spruce and cypress. In a home, the softwoods are used primarily as structural lumber such as 2x4s and 2x6s, with some limited decorative applications. 

Using satellite imaging technology, the Department of Natural Resources has compiled an inventory of every tree standing on a particular day. You are to compute the total fraction of the tree population represented by each species.

输入

Input to your program consists of a list of the species of every tree observed by the satellite; one tree per line. No species name exceeds 30 characters. There are no more than 10,000 species and no more than 1,000,000 trees.

输出

Print the name of each species represented in the population, in alphabetical order, followed by the percentage of the population it represents, to 4 decimal places.

样例输入

Red AlderAshAspenBasswoodAshBeechYellow BirchAshCherryCottonwoodAshCypressRed ElmGumHackberryWhite OakHickoryPecanHard MapleWhite OakSoft MapleRed OakRed OakWhite OakPoplanSassafrasSycamoreBlack WalnutWillow

样例输出

Ash 13.7931Aspen 3.4483Basswood 3.4483Beech 3.4483Black Walnut 3.4483Cherry 3.4483Cottonwood 3.4483Cypress 3.4483Gum 3.4483Hackberry 3.4483Hard Maple 3.4483Hickory 3.4483Pecan 3.4483Poplan 3.4483Red Alder 3.4483Red Elm 3.4483Red Oak 6.8966Sassafras 3.4483Soft Maple 3.4483Sycamore 3.4483White Oak 10.3448Willow 3.4483Yellow Birch 3.4483

提示

This problem has huge input, use scanf instead of cin to avoid time limit exceeded.

分析：

这个题目实际上就是一道模拟题，但是由于数据量很大，所以在搜索的时候需要做优化。如果我们采用二叉搜索，虽然节省了搜索的时间，但是插入新节点的时候需要平移等的操作过于麻烦，所以我们采用二叉搜索树，利用字符串作为关键码值，利用STRCMP函数作为比较的评判标准。

下面来看代码：

#include <iostream>#include <cstring>#include <algorithm>#include <iomanip>using namespace std;struct Node {char name[35];int num;Node *left;Node *right;Node() {name[0] = 0;     //在搜索函数中会看到作用num = 0;left = right = NULL;}};Node *search(char des[], Node *root) {   //在二叉搜索树中找对应字符串所在节点位置Node *tmp = root;while(1) {if (tmp->name[0] == '\0') {   //仅有根节点才会出现的情况strcpy(tmp->name, des);return tmp;} int k = strcmp(des, tmp->name);if (k == 0)           //就是他了！return tmp;if (k < 0) {          //搜索左支if (tmp->left != NULL) {tmp = tmp->left;return search(des, tmp);   //递归查找}else {                             //不可能再找到，说明需要新建节点tmp->left = new Node;      tmp = tmp->left;strcpy(tmp->name, des);return tmp;}}if (k > 0) {          //搜索右支，类似左支if (tmp->right != NULL) {tmp = tmp->right;return search(des, tmp);}else {tmp->right = new Node;tmp = tmp->right;strcpy(tmp->name, des);return tmp;}}}}

//中序遍历二叉搜索树，实现按照字母序打印输出void output(Node *root, int con) {if (root->left != NULL)dfs(root->left, con);double t = 100 * (double)root->num/(double)con;cout << root->name << " ";cout << setiosflags(ios::fixed) << setprecision(4) << t << endl;if (root->right != NULL)dfs(root->right, con);}int main(){Node *root = new Node();Node *tmp;char in[35];int count = 0;   //总共多少树while(gets(in) != NULL) {count++;tmp = search(in, root);tmp->num += 1;}output(root, count);return 0;}