uva_548-Tree

/**中序，后序建树，然后遍历，求根到叶子的最小和，输出
 *该叶子节点，关于通过二叉树建树问题，本博客有相关讲述。。。
 */
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

struct Node {
    int v;
    Node *lc, *rc;
};

#define MAX 10001
#define MAXN 700001
#define INF 0x7fffffff


char str1[MAXN], str2[MAXN];
int order[MAX], post[MAX];
int len, minv, ans;

int find(int c, int pos, int n){
    for(int i = pos; i <= n; i ++){
        if( c == order[i] ) return i;
    }
    return -1;
}

void post_order_create_tree(Node *&root, int r, int m, int length){
	if( length <= 0 ) { root = NULL; return ;}

	root = new Node;
	root->v = post[r];
	int pos = find(post[r], m, length+m);
	int leftlen = pos - m;
	int rightlen = length - leftlen - 1;

	post_order_create_tree(root->lc, r-1-rightlen, m, leftlen);
    post_order_create_tree(root->rc, r-1, pos+1, rightlen);
}

void find_min(Node* root, int sum){
    if( !root ) return;
    sum += root->v;
    if(!root->lc && !root->rc){
    	if(minv > sum){
    		minv = sum;
    		ans = root->v;
    	}else if( minv == sum ){
            ans = min(ans, root->v);
        }
    	return ;
    }
    find_min(root->lc, sum);
    find_min(root->rc, sum);

}

void print(Node *root){
    if( !root ) return ;
    printf("%d ",root->v);
    print(root->lc);
    print(root->rc);
}

int main(int argc, char const *argv[])
{
#ifndef ONLINE_JUDGE
		freopen("test.in", "r", stdin);
		//freopen("test.out", "w", stdout);
#endif
    int length;
    Node *root;
	while( gets(str1) > 0){
	    gets(str2);
	    length = 0;
	     minv = ans = INF;
		for(int i = 0; str1[i] != '\0'; i ++){
		    if( str1[i] == ' ' ) { length ++; continue;}
		    order[length] *= 10;
            order[length] += str1[i] - '0';
		}
		length = 0;
		for(int i = 0; str2[i] != '\0'; i ++){
		    if( str2[i] == ' ' ) { length ++; continue;}
		    post[length] *= 10;
            post[length] += str2[i] - '0';
		}
		length ++;
		len = length;
		post_order_create_tree(root, length-1, 0, length);
        find_min(root, 0);
        printf("%d\n",ans);
        memset(order, 0, sizeof(int) * length);
        memset(post, 0, sizeof(int) * length);
	}
	return 0;
}