https://leetcode.com/problems/increasing-subsequences/
Given an integer array, your task is to find all the different possible increasing subsequences of the given array, and the length of an increasing subsequence should be at least 2 .
Example:
Input: [4, 6, 7, 7] Output: [[4, 6], [4, 7], [4, 6, 7], [4, 6, 7, 7], [6, 7], [6, 7, 7], [7,7], [4,7,7]]Note:
- The length of the given array will not exceed 15.
- The range of integer in the given array is [-100,100].
- The given array may contain duplicates, and two equal integers should also be considered as a special case of increasing sequence.
dfs,針對每一個層級內部記錄並排除重複實現剪枝,前面的子串對後面的子串有完全的覆蓋效果(在同一個層級中)
class Solution {
public:
vector<vector<int>> result;
vector<int> inter;
vector<vector<int>> findSubsequences(vector<int>& nums) {
dfs(0, nums);
return result;
}
void dfs(int pos, vector<int>& nums){
if(inter.size() >= 2) result.push_back(inter);
if(pos >= nums.size()) return;
unordered_map<int, int> used;
for(int i = pos; i < nums.size(); ++i){
if((inter.empty() || nums[i] >= inter.back()) && used.find(nums[i]) == used.end()){
inter.push_back(nums[i]);
dfs(i+1, nums);
inter.pop_back();
used[nums[i]] = 1;
}
}
}
};