题目描述

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 Figure 1: 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 Figure 1.

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 = Bifor 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

代码段

#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
const int maxn = 110;
struct node {
	int weight;
	vector<int> child;
}Node[maxn];

bool cmp(int a, int b) {
	return Node[a].weight > Node[b].weight;
}

int n, m, s;
int path[maxn];

void DFS(int index, int numNode, int sum) {
	if (sum > s)
		return;
	if (sum == s) {
		if (Node[index].child.size() != 0)
			return;
		for (int i = 0; i < numNode; i++){
			printf("%d", Node[path[i]].weight);
			if (i < numNode - 1)
				printf(" ");
			else
				printf("\n");
		}
		return;
	}
	for (int i = 0; i < Node[index].child.size(); i++) {
		int child = Node[index].child[i];
		path[numNode] = child;
		DFS(child, numNode + 1, sum + Node[child].weight);
	}
}

int main() {
	scanf("%d%d%d", &n, &m, &s);
	for (int i = 0; i < n; i++)
		scanf("%d", &Node[i].weight);
	int id, k, child;
	for (int i = 0; i < m; i++) {
		scanf("%d%d", &id, &k);
		for (int j = 0; j < k; j++) {
			scanf("%d", &child);
			Node[id].child.push_back(child);
		}
		sort(Node[id].child.begin(), Node[id].child.end(), cmp);
	}
	path[0] = 0;
	DFS(0, 1, Node[0].weight);
	return 0;
}