POJ2503--神族文字

解析：
先对字符串进行排序，再使用二分查找法即可。
代码：

#include<iostream>
#include <algorithm>
#include<cstdio>
#include<string>
#include<Windows.h>
#include<cstring>
#define MAXN 10010
using namespace std;
struct node 
{
	char a[12];
	char b[12];
}dat[MAXN];
int pos;
char str[24];
int main()
{
	int en, st, mid;
	char val[24];
	pos = 0;
	while (gets_s(str))
	{
		if (str[0] == '\0') break;
		sscanf(str,"%s%s", dat[pos].a, dat[pos].b);	//从空格处拆分成两个字符串
		pos++;
	}
	cin >> val;
	st = 0;
	en = pos - 1;
	sort(str,str+pos);
	while (st <= en)
	{
		mid = (st + en) >> 1;
		if (strcmp(dat[mid].b, val) == 0) {
			cout << dat[mid].a << endl;
			system("pause");
			return 0;
		}
		else if (strcmp(dat[mid].b, val) < 0)
			en = mid - 1;
		else st = mid + 1;
	}
	cout << "not found!" << endl;
	system("pause");
	return 0;
}