poj 1011 Sticks(dfs+剪枝)

http://poj.org/problem?id=1011

　　回归基础，搞一下DFS+剪枝的题。

　　这题的代码打了两次，测了好多组数据才得到AC的代码。两次的代码都是因为返回的时候没有及时将used标记更新，而导致不停的WA。可是第一个代码写的太乱了，debug 漫天飞，于是就决定重新写了一遍。第二次打的时候思路清晰的许多，最后得到下面AC代码~

View Code

  1 #include <cstdio>
  2 #include <cmath>
  3 #include <cstring>
  4 #include <iomanip>
  5 #include <iostream>
  6 #include <algorithm>
  7 #include <vector>
  8 #include <string>
  9 #include <set>
 10 #include <queue>
 11 
 12 using namespace std;
 13 
 14 #define pb push_back
 15 #define fi first
 16 #define se second
 17 #define mpr make_pair
 18 #define _clr(x) memset(x, 0, sizeof(x))
 19 #define _rst(x) memset(x, -1, sizeof(x))
 20 #define REP(i, n) for (int i = 0; i < n; i++)
 21 #define FORI(i, a, b) for (int i = a; i <= b; i++)
 22 #define FORD(i, a, b) for (int i = a; i >= b; i--)
 23 
 24 typedef __int64 ll;
 25 typedef pair<int, int> pii;
 26 typedef vector<ll> vll;
 27 typedef vector<pii> vpii;
 28 typedef vector<int> vi;
 29 typedef vector<double> vdbl;
 30 const int N = 70;
 31 const int hashMod = 1000007;
 32 const int inf = 0x55555555;
 33 const double eps = 1e-8;
 34 const ll linf = 0x5555555555555555ll;
 35 const double finf = 1e50;
 36 const double pi = acos(-1.0);
 37 
 38 int rec[N], n;
 39 bool used[N];
 40 
 41 bool dfs(int p, int g, int G, int s, int S) {
 42 //    cout << p << ends << g << ends << G << ends << s << ends << S << endl;
 43 //    cout << used[0] << endl;
 44     used[p] = true;
 45     if (s == S && g == G) return true;
 46     if (s == S) {
 47         int t = n;
 48         while (t--) {
 49             if (used[t]) continue;
 50 //            cout << "~~~" << t << endl;
 51             if (dfs(t, g + 1, G, rec[t], S)) return true;
 52             else {
 53                 used[p] = false;
 54                 return false;
 55             }
 56         }
 57     }
 58     int t = p;
 59     while (t--) {
 60         if (used[t] || rec[t] + s > S) continue;
 61         if (dfs(t, g, G, rec[t] + s, S)) return true;
 62         while (t && rec[t] == rec[t - 1]) t--;
 63     }
 64     used[p] = false;
 65     return false;
 66 }
 67 
 68 int work() {
 69     int sum = 0;
 70     REP(i, n) {
 71         cin >> rec[i];
 72         sum += rec[i];
 73     }
 74     sort(rec, rec + n);
 75     int mk = sum;
 76 //    REP(i, n) cout << rec[i] << ends;
 77 //    cout << endl;
 78     FORI(i, rec[n - 1], sum - 1) {
 79         _clr(used);
 80         if (sum % i == 0 && dfs(n - 1, 1, sum / i, rec[n - 1], i)) {
 81             mk = i;
 82             break;
 83         }
 84     }
 85     return mk;
 86 }
 87 
 88 int main() {
 89 //    freopen("in", "r", stdin);
 90     while (cin >> n && n) {
 91         cout << work() << endl;
 92     }
 93     return 0;
 94 }
 95 
 96 /*
 97 9
 98 5 2 1 5 2 1 5 2 1
 99 4
100 1 2 3 4
101 64
102 40 40 30 35 35 26 15 40 40 40 40 40 40 40 40 40 40 40 40 40 40
103 40 40 43 42 42 41 10 4 40 40 40 40 40 40 40 40 40 40 40 40 40
104 40 25 39 46 40 10 4 40 40 37 18 17 16 15 40 40 40 40 40 40 40 40
105 64
106 5 8 6 1 4 5 8 2 1 6 4 2 3 6 2 5 8 7 9 2 1 4 3 6 5 4 7 8
107 2 6 5 1 4 5 3 6 5 6 2 1 4 7 8 9 5 2 1 9 4 7 5 2 3 6 9 4
108 5 8 9 2 4 6 3 6
109 3
110 1 5 8
111 9
112 15 3 2 11 4 1 8 8 8
113 0
114 */

——written by Lyon