#22 Flatten List

最新推荐文章于 2022-07-01 20:42:46 发布

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最新推荐文章于 2022-07-01 20:42:46 发布

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分类专栏： lintcode 文章标签： lintcode recursion

本文链接：https://blog.youkuaiyun.com/haifischxia/article/details/52275672

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本文介绍了一种递归方法来解决列表扁平化问题，即如何将嵌套的整数列表转换为简单的一维整数列表。通过具体的代码实现展示了算法的工作原理，并提供了两个实例说明其应用。

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题目描述：

This problem is in a contest: Career Fair Warm Up I . Submit your code and see your ranking!

Given a list, each element in the list can be a list or integer. flatten it into a simply list with integers.

Notice

If the element in the given list is a list, it can contain list too.

Have you met this question in a real interview?

Yes

Example

Given [1,2,[1,2]], return [1,2,1,2].

Given [4,[3,[2,[1]]]], return [4,3,2,1].

Challenge

Do it in non-recursive.

题目思路：

non-recursive我不会做。。下面是我recursive的做法：

Mycode（AC = 489ms）：

/**
 * // This is the interface that allows for creating nested lists.
 * // You should not implement it, or speculate about its implementation
 * class NestedInteger {
 *   public:
 *     // Return true if this NestedInteger holds a single integer,
 *     // rather than a nested list.
 *     bool isInteger() const;
 *
 *     // Return the single integer that this NestedInteger holds,
 *     // if it holds a single integer
 *     // The result is undefined if this NestedInteger holds a nested list
 *     int getInteger() const;
 *
 *     // Return the nested list that this NestedInteger holds,
 *     // if it holds a nested list
 *     // The result is undefined if this NestedInteger holds a single integer
 *     const vector<NestedInteger> &getList() const;
 * };
 */
class Solution {
public:
    // @param nestedList a list of NestedInteger
    // @return a list of integer
    vector<int> flatten(vector<NestedInteger> &nestedList) {
        // Write your code here
        vector<int> ans;
        
        if (nestedList.size() == 0) {
            return ans;
        }
        else {
            for (int i = 0; i < nestedList.size(); i++) {
                if (nestedList[i].isInteger()) {
                    ans.push_back(nestedList[i].getInteger());
                }
                else {
                    vector<NestedInteger> rest = nestedList[i].getList();
                    vector<int> r = flatten(rest);
                    for (int j = 0; j < r.size(); j++) {
                        ans.push_back(r[j]);
                    }
                }
            }
        }
    }
};