uva 548 -Tree

You are to determine the value of the leaf node in a given binary tree that is the terminal node of a path of least value from the root of the binary tree to any leaf. The value of a path is the sum of values of nodes along that path.

Input 

The input file will contain a description of the binary tree given as the inorder and postorder traversal sequences of that tree. Your program will read two line (until end of file) from the input file. The first line will contain the sequence of values associated with an inorder traversal of the tree and the second line will contain the sequence of values associated with a postorder traversal of the tree. All values will be different, greater than zero and less than 10000. You may assume that no binary tree will have more than 10000 nodes or less than 1 node.

Output 

For each tree description you should output the value of the leaf node of a path of least value. In the case of multiple paths of least value you should pick the one with the least value on the terminal node.

Sample Input 

3 2 1 4 5 7 6
3 1 2 5 6 7 4
7 8 11 3 5 16 12 18
8 3 11 7 16 18 12 5
255
255

Sample Output 

1
3
255

根据中序和后序建树，然后右从根扫描到叶，找出值最小的路径，输出叶子节点，这次算是学会如何建树了，还找到了别人写的挺好的模版，算是又熟悉一步吧。

#include <cstdio> 

int inorder[100005],post[100005];
int ans,pos;//ans代表路径总和最小值,pos代表这叶结点 
struct node{
    int num;
    struct node*l;
    struct node*r;
};

struct node*buildtree(int*m,int*p,int len){
    if(len==0)
        return NULL;
    int k=0;
    while(m[k]!=p[len-1])
        k++;
    struct node*root=new node;
    root->num=p[len-1];
    root->l=NULL,root->r=NULL; 
    root->l=buildtree(m,p,k);
    root->r=buildtree(m+k+1,p+k,len-k-1);
    return root;
}

void findmin(struct node*root,int sum){
    if(root==NULL)return;
    sum+=root->num;
    if(root->l==NULL&&root->r==NULL){//如果已经到达叶子节点就比较一下 
        if(sum<ans){
           ans=sum;
           pos=root->num;
        }
        return;
    }
    findmin(root->l,sum);
    findmin(root->r,sum);
}

int main(){
    int n,len;
    char ch;
    while(scanf("%d",&n)!=EOF){
        inorder[0]=n,len=1;                          
        scanf("%c",&ch);
        while(ch!='\n'){
            scanf("%d",&inorder[len++]);
            scanf("%c",&ch);
        }
        for(int i=0;i<len;i++)scanf("%d",&post[i]);
        node*root=new node;
        root->l=NULL,root->r=NULL;
        root=buildtree(inorder,post,len);
        ans=1000000000;
        findmin(root,0);
        printf("%d\n",pos); 
    } 
    return 0;
}