点击链接PAT甲级-AC全解汇总
题目：
Given a non-empty tree with root R, and with weight W?i?? assigned to each tree node T?i? . 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<2?30?? , the given weight number. The next line contains N positive numbers where W?i?? (<1000) corresponds to the tree node T?i?? . 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 {A?1?? ,A?2?? ,?,A?n?? } is said to be greater than sequence {B?1?? ,B?2?? ,?,B?m?? } if there exists 1≤k<min{n,m} such that A?i?? =B?i?? for i=1,?,k, and A?k+1?? >B?k+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
题意：
找到根到叶路径的权重和与目标一样的路径
算法笔记的代码：
#include<cstdio>
#include<vector>
#include<algorithm>
using namespace std;
const int maxn=100;
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(" ");elseprintf("\n");}return;}//↑出口，↓递归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;
}