leetcode40

class Solution {
    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        List<List<Integer>> combinations = new ArrayList<>();
        Arrays.sort(candidates);
        List<Integer> tempCombination = new ArrayList<>();
        backtracking(tempCombination, combinations, new boolean[candidates.length], 0, target, candidates);
        return combinations;
    }

    private void backtracking(List<Integer> tempCombination, List<List<Integer>> combinations,
                              boolean[] hasVisited, int start, int target, final int[] candidates) {

        if (target == 0) {
            combinations.add(new ArrayList<>(tempCombination));
            return;
        }
        for (int i = start; i < candidates.length; i++) {
            if (i != 0 && candidates[i] == candidates[i - 1] && !hasVisited[i - 1]) {
                continue;
            }
            if (candidates[i] <= target) {
                tempCombination.add(candidates[i]);
                hasVisited[i] = true;
                backtracking(tempCombination, combinations, hasVisited, i + 1, target - candidates[i], candidates);
                hasVisited[i] = false;
                tempCombination.remove(tempCombination.size() - 1);
            }
        }
    }
}

对比leetcode39：

public class LEET_39 {
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
        List<List<Integer>> combinations = new ArrayList<>();
        List<Integer> tempCombination = new ArrayList<>();
        backtracking(tempCombination, combinations, 0, target, candidates);
        return combinations;
    }

    private void backtracking(List<Integer> tempCombination, List<List<Integer>> combinations,
                              int start, int target, final int[] candidates) {

        if (target == 0) {
            combinations.add(new ArrayList<>(tempCombination));
            return;
        }
        for (int i = start; i < candidates.length; i++) {
            if (candidates[i] <= target) {
                tempCombination.add(candidates[i]);
                backtracking(tempCombination, combinations, i, target - candidates[i], candidates);
                tempCombination.remove(tempCombination.size() - 1);
            }
        }
    }
}