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​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]
1

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​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
1
2
3
4
5
6
7
8
9
10
11

Sample Output:

10 5 2 7
10 4 10
10 3 3 6 2
10 3 3 6 2
1
2
3
4

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
#include
#include
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(" ");
            else
                printf("\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;
}
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