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L40.java
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L40.java
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package Algorithm;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
/*
* 这道题目还是利用回溯递归的方法
*/
public class L40 {
public List<List<Integer>> combinationSum2(int[] candidates, int target) {
List<List<Integer>> res = new ArrayList<List<Integer>>();
if(candidates == null || candidates.length == 0 || target < 0)
return res;
List<Integer> list = new ArrayList<Integer>();
Arrays.sort(candidates);//因为有重复的数字,所以需要进行排序去重
get(candidates, res, list, target, 0);
return res;
}
private void get(int [] candidates, List<List<Integer>> res, List<Integer> list, int target, int i) {
if(i > candidates.length || target < 0)
return;
if(target == 0) {
res.add(new ArrayList<Integer>(list)); //这里如以前一样需要注意
return;
}
for(int p = i; p < candidates.length; p ++) { //因为这道题目是可以下标不连续,所以需要从i到candidates的最后
list.add(candidates[p]); //添加
get(candidates, res, list, target - candidates[p], p + 1);
list.remove(list.size() - 1); //回溯删除
while(p < candidates.length && candidates[p] == candidates[p + 1]) {
p ++;//去除重复的数字
}
}
}
}