[LeetCode]39. Combination Sum

Problem Description

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:

All numbers (including target) will be positive integers.

Elements in a combination (a1, a2, … , ak) must be in non-descending order. (ie, a1 ≤ a2 ≤ … ≤ ak).

The solution set must not contain duplicate combinations.

For example, given candidate set 2,3,6,7 and target 7,

A solution set is:

[7]

[2, 2, 3]

[]https://leetcode.com/problems/combination-sum/]

思路

先把候选数组排序，然后递归深度搜索就可以了。。。

第一次一遍AC的题，Mark一下！！！！

Code

package Q39;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Solution {

public static void getComb(int[] candidates, int target, List<Integer> tmp,
List<List<Integer>> ans,int j) {
for (int i = j; i < candidates.length; i++) {
if (target == 0) {
ans.add(new ArrayList<Integer>(tmp));
return;
}
if (target < 0 || candidates[i] > target) {
break;
} else {
if (target - candidates[i] >= 0) {
tmp.add(candidates[i]);
getComb(candidates, target - candidates[i], tmp, ans,i);
tmp.remove(tmp.size()-1);
}
}
}

}

public static List<List<Integer>> combinationSum(int[] candidates,
int target) {
List<List<Integer>> ans = new ArrayList<List<Integer>>();
Arrays.sort(candidates);
List<Integer> tmp = new ArrayList<Integer>();
getComb(candidates, target, tmp, ans,0);

return ans;
}

//  public static void main(String[] args) {
//      int[] a = { };
//      System.out.println(combinationSum(a, 1).toString());
//  }

}