1053 Path of Equal Weight(30 分)
Given a non-empty tree with root R, and with weight Wi assigned to each tree node Ti. The weight of a path from R to L is defined to be the sum of the weights of all the nodes along the path from R to any leaf node L.
Now given any weighted tree, you are supposed to find all the paths with their weights equal to a given number. For example, let's consider the tree showed in the following figure: for each node, the upper number is the node ID which is a two-digit number, and the lower number is the weight of that node. Suppose that the given number is 24, then there exists 4 different paths which have the same given weight: {10 5 2 7}, {10 4 10}, {10 3 3 6 2} and {10 3 3 6 2}, which correspond to the red edges in the figure.
Input Specification:
Each input file contains one test case. Each case starts with a line containing 0<N≤100, the number of nodes in a tree, M (<N), the number of non-leaf nodes, and 0<S<230, the given weight number. The next line contains N positive numbers where Wi (<1000) corresponds to the tree node Ti. Then M lines follow, each in the format:
ID K ID[1] ID[2] ... ID[K]
where ID
is a two-digit number representing a given non-leaf node, K
is the number of its children, followed by a sequence of two-digit ID
's of its children. For the sake of simplicity, let us fix the root ID to be 00
.
Output Specification:
For each test case, print all the paths with weight S in non-increasing order. Each path occupies a line with printed weights from the root to the leaf in order. All the numbers must be separated by a space with no extra space at the end of the line.
Note: sequence {A1,A2,⋯,An} is said to be greater than sequence {B1,B2,⋯,Bm} if there exists 1≤k<min{n,m} such that Ai=Bi for i=1,⋯,k, and Ak+1>Bk+1.
Sample Input:
20 9 24
10 2 4 3 5 10 2 18 9 7 2 2 1 3 12 1 8 6 2 2
00 4 01 02 03 04
02 1 05
04 2 06 07
03 3 11 12 13
06 1 09
07 2 08 10
16 1 15
13 3 14 16 17
17 2 18 19
Sample Output:
10 5 2 7
10 4 10
10 3 3 6 2
10 3 3 6 2
C++代码如下:
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
#define maxn 105 struct Node {
int weight;
vector<int>child;
}; int n, m, s;
Node num[maxn]; bool cmp(int a, int b) {
return num[a].weight > num[b].weight;
} vector<int>v; //存放路径对应的权值
void path(int r,int sum) {
if (sum > s) {
v.pop_back(); return;
}
if (sum == s) {
if ( num[r].child.size() == ) {
cout << v[];
for (vector<int>::iterator it = v.begin() + ; it != v.end(); it++)
cout << ' ' << *it;
cout << endl;
v.pop_back();
return;
}
else {
v.pop_back(); return;
}
}
for (int i = ; i < num[r].child.size(); i++) {
int t = num[r].child[i];
v.push_back(num[t].weight);
path(t, sum + num[t].weight);
}
if (!v.empty()) v.pop_back();
}
int main() {
cin >> n >> m >> s;
int w; for (int i = ; i < n; i++) {
cin >> w;
num[i].weight = w;
}
int id,k,t;
for (int i = ; i < m; i++) {
cin >> id>>k;
for (int j = ; j < k; j++) {
cin >> t;
num[id].child.push_back(t);
}
sort(num[id].child.begin(), num[id].child.end(), cmp);
}
v.push_back(num[].weight);
path(,num[].weight);
return ;
}