hello-algo/codes/java/chapter_backtracking/subset_sum_i_naive.java
Yudong Jin a005c6ebd3
Some improvements (#1073)
* Update avatar's link in the landing page

* Bug fixes

* Move assets folder from overrides to docs

* Reduce figures' corner radius

* Update copyright

* Update header image

* Krahets -> krahets

* Update the landing page
2024-02-07 22:21:18 +08:00

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/**
* File: subset_sum_i_naive.java
* Created Time: 2023-06-21
* Author: krahets (krahets@163.com)
*/
package chapter_backtracking;
import java.util.*;
public class subset_sum_i_naive {
/* 回溯算法:子集和 I */
static void backtrack(List<Integer> state, int target, int total, int[] choices, List<List<Integer>> res) {
// 子集和等于 target 时,记录解
if (total == target) {
res.add(new ArrayList<>(state));
return;
}
// 遍历所有选择
for (int i = 0; i < choices.length; i++) {
// 剪枝:若子集和超过 target ,则跳过该选择
if (total + choices[i] > target) {
continue;
}
// 尝试:做出选择,更新元素和 total
state.add(choices[i]);
// 进行下一轮选择
backtrack(state, target, total + choices[i], choices, res);
// 回退:撤销选择,恢复到之前的状态
state.remove(state.size() - 1);
}
}
/* 求解子集和 I包含重复子集 */
static List<List<Integer>> subsetSumINaive(int[] nums, int target) {
List<Integer> state = new ArrayList<>(); // 状态(子集)
int total = 0; // 子集和
List<List<Integer>> res = new ArrayList<>(); // 结果列表(子集列表)
backtrack(state, target, total, nums, res);
return res;
}
public static void main(String[] args) {
int[] nums = { 3, 4, 5 };
int target = 9;
List<List<Integer>> res = subsetSumINaive(nums, target);
System.out.println("输入数组 nums = " + Arrays.toString(nums) + ", target = " + target);
System.out.println("所有和等于 " + target + " 的子集 res = " + res);
System.out.println("请注意,该方法输出的结果包含重复集合");
}
}