POJ 2255 Tree Recovery（树的遍历）

给定前序遍历和中序遍历，写出后序遍历。

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <string>
#include <cmath>
#include <assert.h>
#include <algorithm>
#define MAX 1234567890
#define MIN -1234567890
#define eps 1e-8

using namespace std;

char bef[32];
char mid[32];
char aft[32];
char tree[1024];
bool visit[32];
int len;
int p;

void build(char root, int t)
{
int i, j;
tree[t] = root;
visit[root-'A'] = true;
for(i = 0; i < len; i++) if(mid[i] == root) break;
for(j = 0; j < len; j++) if(bef[j] == root) break;
if(i-1 >= 0 && !visit[mid[i-1]-'A'])
{
char lson = bef[j+1];
build(lson, 2*t);
}
if(i+1 < len && !visit[mid[i+1]-'A'])
{
char rson;
for(int k = j+1; k < len; k++)
{
if(!visit[bef[k]-'A'])
{
rson = bef[k];
break;
}
}
build(rson, 2*t+1);
}
}

void after(char root, int t)
{
if(tree[2*t] != '\0') after(tree[2*t], 2*t);
if(tree[2*t+1] != '\0') after(tree[2*t+1], 2*t+1);
aft[p++] = root;
}

int main()
{
#ifdef BellWind
freopen("2255.in", "r", stdin);
#endif // BellWind

while (~scanf("%s %s", bef, mid))
{
memset(visit, 0, sizeof(visit));
memset(tree, 0, sizeof(tree));
len = strlen(bef);
build(bef[0], 1);
// int cnt = 0;
// for(int c = 1; cnt < len; c++)
// {
// if(tree[c] == '\0') cout << ' ';
// else {cnt++; cout << tree[c];}
// }
// cout << endl;
p = 0;
after(bef[0], 1);
for(int c = 0; c < len; c++) cout << aft[c];
cout << endl;
}

return 0;
}