回溯+剪枝的簡易實現方式,比較典型的39.Combination Sum,在dfs的函數的for循環裏面直接加上判斷來實現剪枝,同時事先sort來去除重複,這道題目其實非常典型。
void DFS(int st, int num, int target, vector<int>& candidates){
if(num == target){
ans.push_back(path);
return;
}
for(int i=st;i<candidates.size()&&num+candidates[i]<=target;i++){
path.push_back(candidates[i]);
DFS(i, num+candidates[i], target, candidates);
path.pop_back();
}
}
vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
path.clear();
ans.clear();
sort(candidates.begin(), candidates.end());
DFS(0, 0, target, candidates);
return ans;
}