Bandwidth UVA - 140 

暴力枚举

刘汝佳书中说了半天如何剪枝，但是他的代码仓库中依旧是暴力枚举

代码参考刘汝佳的代码仓库

#include<iostream>
#include<cmath>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<string>
#include<vector>
#pragma warning(disable:4996)
using namespace std;
int main()
{
	char input[1000], letter[10];
	int id[200];
	while (scanf("%s", input)==1 && input[0] != '#')
	{
		int n = 0;
		for (char ch = 'A'; ch <= 'Z'; ch++)
			if (strchr(input, ch) != NULL) {
				id[ch] = n++;
				letter[id[ch]] = ch;          //建立一个双映射，通过id数组可以找到节点字母对应编号
											  //通过letter数组可以找到编号对应字母
											  //这样做的目的是为了方便输出以及枚举全排列
			}
		//处理输入
		int p = 0, q = 0, len = strlen(input);
		vector<int> u, v;                //存储无向边
		for (;;)
		{
			while (p < len&&input[p] != ':') p++;
			if (p == len) break;
			while (q < len&&input[q] != ';') q++;
			for (int i = p + 1; i < q; i++) {
				u.push_back(id[input[p - 1]]);
				v.push_back(id[input[i]]);
			}	
			p++; q++;
		}
		int P[10], best_P[10], pos[10], ans = n;
		for (int i = 0; i < n; i++) P[i] = i;
		do {
			for (int i = 0; i < n; i++) pos[P[i]] = i;
			int best = 0;
			for (int i = 0; i < u.size(); i++) {
				best = max(best, abs(pos[u[i]] - pos[v[i]]));
				if (best >= ans) break;
			}
			if (best < ans) {
				ans = best;
				memcpy(best_P, P, sizeof(P));
			}
		} while (next_permutation(P, P + n));
		for (int i = 0; i < n; i++) printf("%c ", letter[best_P[i]]);
		printf("-> %d\n", ans);
	}

}