题解 | #牛群分组II#

#include <vector>
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param candidates int整型vector 
     * @param target int整型 
     * @return int整型vector<vector<>>
     */
    void backtrace(vector<int>& candidates, vector<vector<int>>& ans, int sum, int target, int start, vector<int>& path) {
        if (sum == target) {
            ans.push_back(path);
            return;
        }
        int len = candidates.size();
        for (int i = start; i < len; i++) {
            if (sum + candidates[i] <= target) {
                path.push_back(candidates[i]);
                backtrace(candidates, ans, sum + candidates[i], target, i+1, path);
                path.pop_back();
            }
        }
    }

    vector<vector<int> > cowCombinationSum2(vector<int>& candidates, int target) {
        // write code here
        vector<vector<int>> ans;
        vector<int> path;
        backtrace(candidates, ans, 0, target, 0, path);
        return ans;
    }
};