548:Tree

Tree

首先根据中序遍历和后序遍历递归地构造二叉树（后续遍历的最后一个节点为二叉树的根节点），然后前序遍历。

输入有点坑，你说你直接告诉多少个节点多好。。。我想的是先用fets读取整个串，然后用atoi转化为数字，本地运行没问题可是一提交就报错，暂时还没找到原因，大概是因为回车符的问题，参考了别人的输入方法过了，比我的想法要好。

#include<bits/stdc++.h>
using namespace std;
const int maxn = 10000 + 5;
char s[maxn*3];
int W,WS;
struct node{
    int num = -1;
    struct node* left = NULL;
    struct node* right = NULL;
};
node* newnode(){ return new node; }
node* build_tree(int n,int mid[],int late[]){
    if(!n) return NULL;
    node* root = new node;
    int rp = 0;
    root->num = late[n-1];
    while(mid[rp] != late[n-1]) rp++; //find the position of root node in the mid
    root->left = build_tree(rp,mid,late);
    root->right = build_tree(n-rp-1,mid+rp+1,late+rp);
    return root;
}
void pre_travel(node* root,int t){
    t += root->num;
    if(!root->left && !root->right){
        if(t < WS){ WS = t; W = root->num; }
        else if(t == WS && root->num < W) W = root->num;
        return;
    }
    if(root->left) pre_travel(root->left,t);
    if(root->right) pre_travel(root->right,t);
}
int main(){
    freopen("data.in","r",stdin);
    freopen("data.out","w",stdout);
    int mid[maxn],late[maxn];
/*  Runtime Error...  maybe because of fgets
    while(fgets(s,maxn*3,stdin)){
        int n = 0,i = 0,len = strlen(s);

        for(;;){
            while(!isdigit(s[i])) i++;
            if(i >= len) break;
            mid[n++] = atoi(s+i);
            while(isdigit(s[i])) i++;
        }
        for(int i = 0;i < n;i++) scanf("%d",&late[i]);
        node* root = build_tree(n,mid,late);
        W = 1<<30,WS = 1<<30;
        pre_travel(root,0);
        printf("%d\n",W);
        getchar(); //吃掉第二行的回车！！！
    }*/
    char ch;
    while(~ scanf("%d%c", &mid[0], &ch))
    {
        int n = 1;
        for(int i = 1; ch != '\n'; i++)
            scanf("%d%c", mid + i, &ch), n++;
        ch = ' ';
        for(int i = 0; ch != '\n'; i++)
            scanf("%d%c", late + i, &ch);
        node* root = build_tree(n,mid,late);
        W = 1<<30,WS = 1<<30;
        pre_travel(root,0);
        printf("%d\n",W);
    }
    return 0;
}