stack+DFS ZOJ 1004 Anagrams by Stack

 /*
stack 容器的应用：    要求字典序升序输出，所以先搜索入栈的
然后逐个判断是否满足答案，若不满足，回溯继续搜索，输出所有符合的结果
*/
#include <cstdio>
#include <iostream>
#include <algorithm>
#include <stack>
#include <cmath>
#include <cstring>
#include <vector>
using namespace std;

const int MAXN = 1e4 + 10;
const int INF = 0x3f3f3f3f;

string s1, s2;
int len;
stack<char> S;
vector<char> V;

void DFS(int push, int pop)
{
if (push == len && pop == len)
{
for (int i=0; i<V.size (); ++i)
cout << V[i] << " ";
cout << endl;
}

if (push + 1 <= len)        //入栈
{
S.push (s1[push]);
V.push_back ('i');
DFS (push+1, pop);
S.pop ();
V.pop_back ();
}

if (pop + 1 <= push && pop + 1 <= len && S.top () == s2[pop])        //出栈
{
char ch = S.top ();
S.pop ();
V.push_back ('o');
DFS (push, pop+1);
S.push (ch);
V.pop_back ();
}
}

int main(void)        //ZOJ 1004 Anagrams by Stack
{
//freopen ("ZOJ_1004.in", "r", stdin);

while (cin >> s1 >> s2)
{
V.clear ();
while (!S.empty ())    S.pop ();

len = s1.length ();

cout << "[" << endl;
DFS (0, 0);
cout << "]" << endl;
}

return 0;
}

/*
[
i i i i o o o i o o
i i i i o o o o i o
i i o i o i o i o o
i i o i o i o o i o
]
[
i o i i i o o i i o o o
i o i i i o o o i o i o
i o i o i o i i i o o o
i o i o i o i o i o i o
]
[
]
[
i i o i o i o o
]
*/