Time Limit: 1000MS | Memory Limit: 10000K | |
Total Submissions: 12681 | Accepted: 4597 |
Description
Unfortunately, as it used to happen in royal families, the son was a little retarded. After many years of study he was able just to add integer numbers and to compare whether the result is greater or less than a given integer number. In addition, the numbers had to be written in a sequence and he was able to sum just continuous subsequences of the sequence.
The old king was very unhappy of his son. But he was ready to make everything to enable his son to govern the kingdom after his death. With regards to his son's skills he decided that every problem the king had to decide about had to be presented in a form of a finite sequence of integer numbers and the decision about it would be done by stating an integer constraint (i.e. an upper or lower limit) for the sum of that sequence. In this way there was at least some hope that his son would be able to make some decisions.
After the old king died, the young king began to reign. But very soon, a lot of people became very unsatisfied with his decisions and decided to dethrone him. They tried to do it by proving that his decisions were wrong.
Therefore some conspirators presented to the young king a set of problems that he had to decide about. The set of problems was in the form of subsequences Si = {aSi, aSi+1, ..., aSi+ni} of a sequence S = {a1, a2, ..., an}. The king thought a minute and then decided, i.e. he set for the sum aSi + aSi+1 + ... + aSi+ni of each subsequence Si an integer constraint ki (i.e. aSi + aSi+1 + ... + aSi+ni < ki or aSi + aSi+1 + ... + aSi+ni > ki resp.) and declared these constraints as his decisions.
After a while he realized that some of his decisions were wrong. He could not revoke the declared constraints but trying to save himself he decided to fake the sequence that he was given. He ordered to his advisors to find such a sequence S that would satisfy the constraints he set. Help the advisors of the king and write a program that decides whether such a sequence exists or not.
Input
Output
Sample Input
4 2 1 2 gt 0 2 2 lt 2 1 2 1 0 gt 0 1 0 lt 0 0
Sample Output
lamentable kingdom successful conspiracy
/*http://blog.csdn.Net/wangjian8006
题目大意:现在假设有一个这样的序列,S={a1,a2,a3,a4...ai...at}
其中ai=a*si,其实这句可以忽略不看
现在给出一个不等式,使得ai+a(i+1)+a(i+2)+...+a(i+n)<ki或者是ai+a(i+1)+a(i+2)+...+a(i+n)>ki
首先给出两个数分别代表S序列有多少个,有多少个不等式
不等式可以这样描述
给出四个参数第一个数i可以代表序列的第几项,然后给出n,这样前面两个数就可以描述为ai+a(i+1)+...a(i+n),即从i到n的连续和,再给出一个符号和一个ki
当符号为gt代表‘>’,符号为lt代表‘<'
那么样例可以表示
1 2 gt 0
a1+a2+a3>0
2 2 lt 2
a2+a3+a4<2
最后问你所有不等式是否都满足条件,若满足输出lamentable kingdom,不满足输出successful conspiracy,这里要注意了,不要搞反了
解题思路:一个典型的差分约束,很容易推出约束不等式
首先设Si=a1+a2+a3+...+ai
那么根据样例可以得出
S3-S0>0---->S0-S3<=-1
S4-S1<2---->S4-S1<=1
因为差分约束的条件是小于等于,所以我们将ki-1可以得到一个等于号
那么通式可以表示为
a b gt c
S[a-1]-s[a+b]<=-ki-1
a b lt c
S[a+b]-S[a-1]<=ki-1
那么根据差分约束建图,加入这些有向边
gt: <a+b,a-1>=-ki-1
lt: <a-1,a+b>=ki-1
再根据bellman_ford判断是否有无负环即可
若出现负环了则这个序列不满足所有的不等式
我写的代码:
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <queue>
#include <iostream>
#define M 301
using namespace std;
const int inf = (1<<25);
struct node
{
int to, dist;
int next;
}E[4*M];
int head[M], dis[M];
bool vis[M];
int sum[M];
int n, m, top;
void init()
{
memset ( head, -1, sizeof(head) );
memset ( vis, false, sizeof(vis) );
memset ( dis, 0, sizeof(dis) );
memset ( sum, 0, sizeof(sum) );
top = 0;
}
void AddEdge(int u, int v, int dist)
{
E[top].to = v;
E[top].dist = dist;
E[top].next = head[u];
head[u] = top++;
}
bool SPFA()
{
int i;
queue<int> q;
for ( i = 0;i <= n+1; i++ )
q.push(i);
vis[0] = true;
while ( !q.empty() )
{
int u = q.front();
q.pop();
vis[u] = false;
for ( i = head[u];i != -1; i = E[i].next )
{
int v = E[i].to;
if ( dis[v] > dis[u]+E[i].dist )
{
dis[v] = dis[u]+E[i].dist;
if ( !vis[v] )
{
vis[v] = true;
q.push(v);
sum[v]++;
if ( sum[v] > n+1 )
return false;
}
}
}
}
return true;
}
int main()
{
int i;
char ch[5];
int u, v, dist;
while ( ~scanf ( "%d", &n ) && n != 0 )
{
init();
scanf ( "%d", &m );
for ( i = 0;i < m; i++ )
{
scanf ( "%d %d %s %d", &u, &v, ch, &dist );
if ( ch[0] == 'g' )
AddEdge(u+v+1, u, -dist-1);
else
AddEdge(u, u+v+1, dist-1);
}
printf ( !SPFA() ? "successful conspiracy\n" : "lamentable kingdom\n" );
}
}
代码菜鸟,如有错误,请多包涵!!!
如有帮助记得支持我一下,谢谢!!!