题目:
我刚开始的代码(能AC):
class Solution {
public:
vector<string> Permutation(string str) {
vector<string> v;
if(str.empty())
return v;
return permuta(v,str,0);
}
vector<string> permuta(vector<string> &v,string str,int n)
{
if(n==str.size())
v.push_back(str);
else
{
permuta(v,str,n+1);
for(int i=n+1;i<str.size();i++)
{
if(str[i]!=str[n])
{
swap(str[n],str[i]);
permuta(v,str,n+1);
}
}
}
return v;
}
};
之后修改的代码,符合逻辑也能AC,想不通第一种为什么能直接实现全排列了
class Solution {
public:
vector<string> Permutation(string str) {
vector<string> v;
if(str.empty())
return v;
permuta(v,str,0);
sort(v.begin(),v.end());
return v;
}
void permuta(vector<string> &v,string str,int n)
{
if(n==str.size())
v.push_back(str);
else
{
permuta(v,str,n+1);
for(int i=n+1;i<str.size();i++)
{
if(str[i]!=str[n])
{
swap(str[n],str[i]);
permuta(v,str,n+1);
swap(str[n],str[i]);
}
}
}
}
};
VS2019中能直接测试的代码放在下面:
#include <bits/stdc++.h>
using namespace std;
vector<string> v;
vector<string> permuta(vector<string>& v, string str, int n);
vector<string> Permutation(string str)
{
if (str.empty())
return v;
return permuta(v, str, 0);
}
vector<string> permuta(vector<string>& v, string str, int n)
{
if (n == str.size())
v.push_back(str);
else
{
permuta(v, str, n + 1);
for (int i = n + 1; i < str.size(); i++)
{
if (str[i] != str[n])
{
swap(str[n], str[i]);
permuta(v, str, n + 1);
//swap(str[n], str[i]);
}
}
}
return v;
}
int main()
{
Permutation("abcd");
return 0;
}
为什么更少的代码也AC了