hdu 4848 Wow! Such Conquering! （floyd dfs）

Wow! Such Conquering!

Problem Description

There are n Doge Planets in the Doge Space. The conqueror of Doge Space is Super Doge, who is going to inspect his Doge Army on all Doge Planets. The inspection starts from Doge Planet 1 where DOS (Doge Olympic Statue) was built. It takes Super Doge exactly T_xy time to travel from Doge Planet x to Doge Planet y.
With the ambition of conquering other spaces, he would like to visit all Doge Planets as soon as possible. More specifically, he would like to visit the Doge Planet x at the time no later than Deadline_x. He also wants the sum of all arrival time of each Doge Planet to be as small as possible. You can assume it takes so little time to inspect his Doge Army that we can ignore it.

Input

There are multiple test cases. Please process till EOF.
Each test case contains several lines. The first line of each test case contains one integer: n, as mentioned above, the number of Doge Planets. Then follow n lines, each contains n integers, where the y-th integer in the x-th line is T_xy . Then follows a single line containing n - 1 integers: Deadline₂ to Deadline_n.
All numbers are guaranteed to be non-negative integers smaller than or equal to one million. n is guaranteed to be no less than 3 and no more than 30.

Output

If some Deadlines can not be fulfilled, please output “-1” (which means the Super Doge will say “WOW! So Slow! Such delay! Much Anger! . . . ” , but you do not need to output it), else output the minimum sum of all arrival time to each Doge Planet.

Sample Input

4
0 3 8 6
4 0 7 4
7 5 0 2
6 9 3 0
30 8 30
4
0 2 3 3
2 0 3 3
2 3 0 3
2 3 3 0
2 3 3

Sample Output

36
-1
暴力搜索，剪枝

view code#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cstdio>
using namespace std;
#define REP(i,n) for(int i=0; i<(n); i++)
#define FOR(i,s,t) for(int i=(s); i<=(t); i++)
const int INF = 1<<30;
const int N = 35;
int dist[N][N], tm[N], n;
int bit[N], tot, ans;

void floyd()
{
    REP(k,n) REP(i,n) REP(j,n) dist[i][j] = min(dist[i][j], dist[i][k]+dist[k][j]);
}

void dfs(int u, int s, int cost, int sum, int num)
{
    if(sum>=ans) return ;
    if(s == tot){
        ans = min(ans, sum);
        return ;
    }
    FOR(i,1,n-1){
        if(s&bit[i]) continue;
        if(cost+dist[u][i]>tm[i]) return ;
    }
    FOR(i,1,n-1){
        if(s&bit[i]) continue;
        dfs(i,  s|bit[i], cost+dist[u][i], sum+num*dist[u][i], num-1);
    }
}

void solve()
{
    REP(i,n) REP(j,n) scanf("%d", &dist[i][j]);
    floyd();
    FOR(i,1,n-1) scanf("%d", tm+i);
    ans = INF, tot = bit[n]-1;
    dfs(0, 1, 0, 0, n-1);
    if(ans==INF) ans=-1;
    printf("%d\n",ans);
}

int main()
{
//    freopen("in.txt", "r", stdin);
    REP(i,31) bit[i] = 1<<i;
    while(scanf("%d", &n)>0) solve();
    return 0;
}