二叉搜索树 POJ 2418 Hardwood Species

题目传送门

题意:输入一大堆字符串,问字典序输出每个字符串占的百分比

分析:二叉搜索树插入,然后中序遍历就是字典序,这里root 被new出来后要指向NULL,RE好几次.这题暴力sort也是可以过的...

//#include <bits/stdc++.h>
#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
struct BST {
    char name[55];
	int cnt;
    BST *lch, *rch;
    BST *insert(BST *p, char *s) {
        if (p == NULL)  {
            BST *t = new BST;
            strcpy (t->name, s);
			t->cnt = 1;
            t->lch = t->rch = NULL;
            return t;
        }
		else if (strcmp (s, p->name) == 0)	{
			(p->cnt)++;
		}
		else if (strcmp (s, p->name) < 0)    p->lch = insert (p->lch, s);
        else    p->rch = insert (p->rch, s);
        return p;
    }
	void mid_travel(BST *p, int n)	{
		if (p != NULL)	{
			mid_travel (p->lch, n);
			if (p->cnt != 0)	printf ("%s %.4f\n", p->name, p->cnt * 1.0 / n * 100);
			mid_travel (p->rch, n);
		}
	}
}bst;

int main(void)	{
	int n = 0;
	char str[55];
	BST *root = new BST;
	root = NULL;
	while (gets (str)) 	{
		root = bst.insert (root, str);	n++;
	}
	bst.mid_travel (root, n);

	return 0;
}

　　

sort

#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;

int n;
struct Name	{
	char str[33];
}name[1000010];

bool cmp(Name a, Name b)	{
	return strcmp (a.str, b.str) < 0;
}

int main(void)	{
	n = 0;
	while (gets (name[n++].str));
	sort (name, name+n, cmp);
	int i = 1;
	while (i < n)	{
		int j = i;
		while (j < n && strcmp (name[j].str, name[i].str) == 0)	j++;
		printf ("%s %.4f\n", name[i].str, (j - i) * 1.0 / (n-1) * 100);
		i = j;
	}

	return 0;
}