leetcode：216. 组合总和 III - 力扣（LeetCode）
class Solution {
List<List<Integer>> res = new ArrayList<>();
LinkedList<Integer> link = new LinkedList<>();
public List<List<Integer>> combinationSum3(int k, int n) {
backtracking(k,n,0,1);
return res;
}
public void backtracking(int k , int n , int sum , int strartIndex){
if( sum > n) return;
if(link.size() > k) return;
//和等于目标值，存入二维数组
if (link.size() == k){
if(sum == n){
res.add(new ArrayList<>(link));
return;
}
}
for(int i = strartIndex;i <= 9; i++){
link.add(i);
sum += i;
backtracking(k,n,sum,i+1);
sum -= i;
link.removeLast();
}
}
}
leetcode：17. 电话号码的字母组合 - 力扣（LeetCode）
class Solution {
List<String> list = new ArrayList<>();
public List<String> letterCombinations(String digits) {
if(digits == null || digits.length() == 0){
return list;
}
String []numString={"","","abc","def","ghi","jkl","mno","pqrs","tuv","wxyz"};
backtracking(digits,numString,0);
return list;
}
StringBuilder temp = new StringBuilder();
public void backtracking(String dights,String[] numString,int num ){
if(num == dights.length()){
list.add(temp.toString());
return;
}
String str = numString[dights.charAt(num) - '0'];
for (int i =0 ; i < str.length(); i++){
temp.append(str.charAt(i));
backtracking(dights,numString,num+1);
temp.deleteCharAt(temp.length() - 1);
}
}
}
标签：216,return,String,int,随想录,字母组合,new,numString,backtracking From： https://www.cnblogs.com/lengbo/p/18091303