完成日期：7月23日
今日总结：
77. 组合
// 递归，好好看看
class Solution {
private:
vector<vector<int>> result;
vector<int> path;
void backtracking(int n, int k, int startIndex){
if(path.size() == k){
result.push_back(path);
return;
}
for(int i = startIndex; i<=n-(k-path.size())+1; ++i){
path.push_back(i);
backtracking(n, k, i+1);
path.pop_back();
}
}
public:
vector<vector<int>> combine(int n, int k) {
backtracking(n, k, 1);
return result;
}
};
46. 全排列
class Solution {
private:
vector<vector<int>> result;
vector<int> path;
void backtracking(vector<int>& nums, vector<bool>& used){
if(path.size()==nums.size()){
result.push_back(path);
return;
}
for(int i =0; i<nums.size(); ++i){
if (used[i] == true) continue;
used[i] = true;
path.push_back(nums[i]);
backtracking(nums, used);
path.pop_back();
used[i] = false;
}
}
public:
vector<vector<int>> permute(vector<int>& nums) {
result.clear();
path.clear();
vector<bool> used(nums.size(), false);
backtracking(nums, used);
return result;
}
};
784. 字母大小写全排列
先不做
