uva1423(拓扑排序)
Given a sequence of integers, a1, a2,..., an , we define its sign matrix S such that, for 1ijn , Sij = `` + "if Sij = `` - " if ai +...+ aj < 0 ; and Sij = ``0" otherwise.
For example, if (a1, a2, a3, a4) = (- 1, 5, - 4, 2) , then its sign matrix S is a 4×4 matrix:
1 | 2 | 3 | 4 | |
1 | - | + | 0 | + |
2 | + | + | + | |
3 | - | - | ||
4 | + |
We say that the sequence (-1, 5, -4, 2) generates the sign matrix. A sign matrix is valid if it can be generated by a sequence of integers.
Given a sequence of integers, it is easy to compute its sign matrix. This problem is about the opposite direction: Given a valid sign matrix, find a sequence of integers that generates the sign matrix. Note that two or more different sequences of integers can generate the same sign matrix. For example, the sequence (-2, 5, -3, 1) generates the same sign matrix as the sequence (-1,5, -4,2).
Write a program that, given a valid sign matrix, can find a sequence of integers that generates the sign matrix. You may assume that every integer in a sequence is between -10 and 10, both inclusive.
Input
Your program is to read from standard input. The input consists of T test cases. The number of test cases T is given in the first line of the input. Each test case consists of two lines. The first line contains an integer n (1n10) , where n is the length of a sequence of integers. The second line contains a string of n(n + 1)/2characters such that the first n characters correspond to the first row of the sign matrix, the next n - 1 characters to the second row, ... , and the last character to the n -th row.
Output
Your program is to write to standard output. For each test case, output exactly one line containing a sequence of n integers which generates the sign matrix. If more than one sequence generates the sign matrix, you may output any one of them. Every integer in the sequence must be between -10 and 10, both inclusive.
Sample Input
3 4 -+0++++--+ 2 +++ 5 ++0+-+-+--+-+--
Sample Output
-2 5 -3 1 3 4 1 2 -3 4 -5
这道题很容易转化成:
已知s[0],s[1]...s[n]的大小关系,求a[1],a[2]...a[n]的值
不要想直接转化得到数列a的大小关系,那样不好找。而已知s后,可以直接用s[n]-s[n-1]求a[n];
并且只要让相邻的s相差为1,a的值的绝对值就不会超过10.
然后拓扑排序时先找到所有入度为0的点后,再进行“减度”。
不过要注意我们的s[0]一样也作为图中的一个点来参与计算,不能当做0 。。。
#include <iostream> #include <stdio.h> #include <stdlib.h> #include<string.h> #include<algorithm> #include<math.h> #include<queue> using namespace std; typedef long long ll; int rd[11],tu[11][11],s[11],aa[11]; void topu(int n) { int oo=-10,flag=1; while(flag) { flag=0; queue<int>q; for(int i=0; i<=n; i++) if(rd[i]==0) { rd[i]--; flag=1; q.push(i); s[i]=oo; } oo++; while(!q.empty()) { int t=q.front(); q.pop(); for(int i=0; i<=n; i++) if(tu[t][i]) rd[i]--; } } //for(int i=0;i<=n;i++) // printf("%d ",s[i]);puts(""); } int main() { int t; scanf("%d",&t); while(t--) { memset(rd,0,sizeof(rd)); memset(tu,0,sizeof(tu)); int n; scanf("%d",&n); for(int i=1; i<=n; i++) for(int j=i; j<=n; j++) { char a; scanf(" %c",&a); if(a=='+') tu[i-1][j]=1,rd[j]++; else if(a=='-') tu[j][i-1]=1,rd[i-1]++; } topu(n); for(int i=1; i<n; i++) { aa[i]=s[i]-s[i-1]; printf("%d ",aa[i]); } printf("%d\n",s[n]-s[n-1]); } return 0; }