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Update the code of permutations i and ii

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krahets
2023-04-27 01:18:18 +08:00
parent 918380b56a
commit 3f430fb85e
7 changed files with 91 additions and 60 deletions
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27
codes/cpp/chapter_backtracking/permutations_i.cpp
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@ -18,26 +18,31 @@ void backtrack(vector<int> &state, const vector<int> &choices, vector<bool> &sel
int choice = choices[i];
// 剪枝：不允许重复选择元素 且 不允许重复选择相等元素
if (!selected[i]) {
// 尝试
selected[i] = true; // 做出选择
state.push_back(choice); // 更新状态
// 尝试：做出选择，更新状态
selected[i] = true;
state.push_back(choice);
backtrack(state, choices, selected, res);
// 回退
selected[i] = false; // 撤销选择
state.pop_back(); // 恢复到之前的状态
// 回退：撤销选择，恢复到之前的状态
selected[i] = false;
state.pop_back();
}
}
}
/* 全排列 I */
vector<vector<int>> permutationsI(vector<int> nums) {
vector<int> state;
vector<bool> selected(nums.size(), false);
vector<vector<int>> res;
backtrack(state, nums, selected, res);
return res;
}
/* Driver Code */
int main() {
vector<int> nums = {1, 2, 3};
// 回溯算法
vector<int> state;
vector<bool> selected(nums.size(), false);
vector<vector<int>> res;
backtrack(state, nums, selected, res);
vector<vector<int>> res = permutationsI(nums);
cout << "输入数组 nums = ";
printVector(nums);

27
codes/cpp/chapter_backtracking/permutations_ii.cpp
View File

@ -19,27 +19,32 @@ void backtrack(vector<int> &state, const vector<int> &choices, vector<bool> &sel
int choice = choices[i];
// 剪枝：不允许重复选择元素 且 不允许重复选择相等元素
if (!selected[i] && duplicated.find(choice) == duplicated.end()) {
// 尝试
// 尝试：做出选择，更新状态
duplicated.emplace(choice); // 记录选择过的元素值
selected[i] = true; // 做出选择
state.push_back(choice); // 更新状态
selected[i] = true;
state.push_back(choice);
backtrack(state, choices, selected, res);
// 回退
selected[i] = false; // 撤销选择
state.pop_back(); // 恢复到之前的状态
// 回退：撤销选择，恢复到之前的状态
selected[i] = false;
state.pop_back();
}
}
}
/* 全排列 II */
vector<vector<int>> permutationsII(vector<int> nums) {
vector<int> state;
vector<bool> selected(nums.size(), false);
vector<vector<int>> res;
backtrack(state, nums, selected, res);
return res;
}
/* Driver Code */
int main() {
vector<int> nums = {1, 1, 2};
// 回溯算法
vector<int> state;
vector<bool> selected(nums.size(), false);
vector<vector<int>> res;
backtrack(state, nums, selected, res);
vector<vector<int>> res = permutationsII(nums);
cout << "输入数组 nums = ";
printVector(nums);