LeetCode演算法題47:全排列 II解析
阿新 • • 發佈:2019-01-03
給定一個可包含重複數字的序列,返回所有不重複的全排列。
示例:
輸入: [1,1,2]
輸出:
[
[1,1,2],
[1,2,1],
[2,1,1]
]
這個題和上一個題全排列是一樣的,只是在判斷條件中在加一些防止重複元素重複出現的元素就可以了。這裡加到最裡面。
C++原始碼:
class Solution {
public:
vector<vector<int>> permuteUnique(vector<int>& nums) {
vector<vector<int >> res;
vector<int> out;
vector<int> flag(nums.size(), 0);
sort(nums.begin(), nums.end());
permuteUniqueDFS(nums, 0, flag, out, res);
return res;
}
void permuteUniqueDFS(vector<int>& nums, int layer, vector<int>& flag, vector<int>& out, vector<vector<int>>& res)
{
if(layer>=nums.size()) res.push_back(out);
else
{
for(int i=0;i<nums.size();i++)
{
if(flag[i]==0)
{
if(i>0 && nums[i]==nums[i-1] && flag[i-1]==0) continue;
out.push_back(nums[i]);
flag[i] = 1;
permuteUniqueDFS(nums, layer+1, flag, out, res);
out.pop_back();
flag[i] = 0;
}
}
}
}
};
python3原始碼:
class Solution:
def permuteUnique(self, nums):
"""
:type nums: List[int]
:rtype: List[List[int]]
"""
res = []
out = []
flag = [0 for i in range(len(nums))]
nums.sort()
self.permuteUniqueDFS(nums, 0, flag, out, res)
return res
def permuteUniqueDFS(self, nums, layer, flag, out, res):
if layer >= len(nums):
res.append(copy.deepcopy(out))
else:
for i in range(len(nums)):
if flag[i] == 0:
if i>0 and nums[i]==nums[i-1] and flag[i-1]==0:
continue
out.append(nums[i])
flag[i] = 1
self.permuteUniqueDFS(nums, layer+1, flag, out, res)
out.pop()
flag[i] = 0