842. Split Array into Fibonacci Sequence_842. split array into fibonacci sequence python-优快云博客

本文介绍了一种算法，用于将给定的数字字符串拆分成一个类似于斐波那契数列的序列。该算法通过深度优先搜索实现，并确保每个数字都符合32位有符号整数的要求。

Given a string S of digits, such as S = "123456579", we can split it into a Fibonacci-like sequence [123, 456, 579].

Formally, a Fibonacci-like sequence is a list F of non-negative integers such that:

0 <= F[i] <= 2^31 - 1, (that is, each integer fits a 32-bit signed integer type);
F.length >= 3;
and F[i] + F[i+1] = F[i+2] for all 0 <= i < F.length - 2.

Also, note that when splitting the string into pieces, each piece must not have extra leading zeroes, except if the piece is the number 0 itself.

Return any Fibonacci-like sequence split from S, or return [] if it cannot be done.

Example 1:

Input: "123456579"
Output: [123,456,579]

Example 2:

Input: "11235813"
Output: [1,1,2,3,5,8,13]

Example 3:

Input: "112358130"
Output: []
Explanation: The task is impossible.

Example 4:

Input: "0123"
Output: []
Explanation: Leading zeroes are not allowed, so "01", "2", "3" is not valid.

Example 5:

Input: "1101111"
Output: [110, 1, 111]
Explanation: The output [11, 0, 11, 11] would also be accepted.

Note:

1 <= S.length <= 200
S contains only digits.

直接DFS求解，一次WA，因为没有注意到int的取值范围

class Solution {
public:
	vector<int> splitIntoFibonacci(string S) {
		vector<int>buffer;
		for (const char& c : S)buffer.push_back(c - '0');
		vector<int>ret;
		dfs(buffer, ret, 0);
		return ret;
	}
private:
	inline int to_int(const vector<int>& buffer, int start, int end) {
		if (buffer[start] == 0 && end - start != 0)return -1;
		int ret = 0;
		for (int i = start; i <= end; ++i) {
			if (ret>INT_MAX / 10)return -1;
			ret *= 10;
			ret += buffer[i];
		}
		return ret;
	}
	bool dfs(const vector<int>& buffer, vector<int>& ret, int level) {
		int len = ret.size();

		if (len >= 3 && ret[len - 2] + ret[len - 3] != ret[len - 1])return false;
		if (level >= buffer.size() && ret.size()<3)return false;
		if (level >= buffer.size() && ret.size() >= 3)return true;

		for (int i = level; i<buffer.size(); ++i) {
			int temp = to_int(buffer, level, i);
			if (temp == -1)continue;
			ret.push_back(temp);
			if (dfs(buffer, ret, i + 1))return true;
			ret.pop_back();
		}
		return false;
	}
};