Leetcode 039 Combination Sum（隐式图搜索）

题目连接：Leetcode 039 Combination Sum

解题思路：隐式图搜索，状态包括当前使用到的数值下标（对应值一定使用过），和剩余的和。每次枚举当前下标往后的一个数，并枚举使用它的个数，对每个合理状态插入队列。而当剩余的和为零时，记录答案。

class Solution {
	public:
		vector> combinationSum(vector& candidates, int target) {
			vector tmp;
			vector> ans;

			queue< pair > que_infos;
			queue> que_state;
			que_infos.push(make_pair(target, 0));
			que_state.push(tmp);

			sort(candidates.begin(), candidates.end());

			while (!que_infos.empty()) {
				int res = que_infos.front().first;
				int start = que_infos.front().second;
				vector state = que_state.front();
				que_infos.pop(), que_state.pop();

				if (res == 0) { ans.push_back(state); continue;}

				for (int i = start; i < candidates.size(); i++) {
					if (candidates[i] > res) break;
					tmp = state;
					tmp.push_back(candidates[i]);
					que_infos.push(make_pair(res - candidates[i], i));
					que_state.push(tmp);
				}
			}

			return ans;
		}
};