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Permutations II.cpp
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88 lines (75 loc) · 2.4 KB
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// http://oj.leetcode.com/problems/permutations-ii/
// Do not need any additional data structure
class Solution {
bool contains_dup(vector<int> &num, int from, int to, int value) {
for (int i = from; i <= to; i++) {
if (num[i] == value) {
return true;
}
}
return false;
}
void do_permute(vector<vector<int> > &ret, vector<int> &buf, vector<int> &num, int left) {
if (left == 0) {
ret.push_back(buf);
return;
}
for (int i = 0; i < left; i++) {
if (!contains_dup(num, 0, i - 1, num[i])) {
buf.push_back(num[i]);
swap(num[i], num[left - 1]);
do_permute(ret, buf, num, left - 1);
swap(num[i], num[left - 1]);
buf.pop_back();
}
}
}
public:
vector<vector<int> > permuteUnique(vector<int> &num) {
vector<vector<int> > ret;
vector<int> buf;
int size = num.size();
if (size <= 0) {
return ret;
}
do_permute(ret, buf, num, size);
return ret;
}
};
// Use additional array to record whether a slot has been used in one function call
class Solution {
void do_permute(vector<vector<int> > &ret, vector<int> &num, vector<int> &buf,
vector<int> &visited, int begin) {
if (begin == num.size()) {
ret.push_back(buf);
return;
}
for (int i = 0; i < num.size(); i++) {
if (visited[i] == 1) {
// remember we always scan from the beginning
continue;
}
if (i > 0 && num[i] == num[i - 1] && visited[i - 1] == 0) {
continue;
}
int t = num[i];
buf.push_back(t);
visited[i] = 1;
do_permute(ret, num, buf, visited, begin + 1);
visited[i] = 0;
buf.pop_back();
}
}
public:
vector<vector<int> > permuteUnique(vector<int> &num) {
if (num.size() == 0) {
return {{}};
}
vector<vector<int> > ret;
vector<int> buf;
vector<int> visited(num.size(), 0);
sort(num.begin(), num.end());
do_permute(ret, num, buf, visited, 0);
return ret;
}
};