花花酱 LeetCode 306. Additive Number

zxi — Sat, 14 Mar 2020 07:38:00 +0000

Additive number is a string whose digits can form additive sequence.

A valid additive sequence should contain at least three numbers. Except for the first two numbers, each subsequent number in the sequence must be the sum of the preceding two.

Given a string containing only digits '0'-'9', write a function to determine if it’s an additive number.

Note: Numbers in the additive sequence cannot have leading zeros, so sequence 1, 2, 03 or 1, 02, 3 is invalid.

Example 1:

Input: "112358"
Output: true
Explanation: The digits can form an additive sequence: 1, 1, 2, 3, 5, 8. 
             1 + 1 = 2, 1 + 2 = 3, 2 + 3 = 5, 3 + 5 = 8

Example 2:

Input: "199100199"
Output: true
Explanation: The additive sequence is: 1, 99, 100, 199. 
             1 + 99 = 100, 99 + 100 = 199

Constraints:

num consists only of digits '0'-'9'.
1 <= num.length <= 35

Solution: DFS

Time complexity: O(n^2)
Space complexity: O(n)

C++

using SV = std::string_view;
class Solution {
public:
  bool isAdditiveNumber(SV s) {    
    auto add = [](SV s1, SV s2) {
      const int l1 = s1.length(), l2 = s2.length();
      string s3(max(l1, l2) + 1, '0');      
      for (int i = 0; i < s3.size() - 1; ++i) {
        int n1 = i < l1 ? s1[l1 - i - 1] - '0' : 0;
        int n2 = i < l2 ? s2[l2 - i - 1] - '0' : 0;
        s3[i] += n1 + n2;
        if (s3[i] > '9') {
          s3[i] -= 10;
          ++s3[i + 1];
        }
      }
      while (s3.back() == '0' && s3.length() > 1) s3.pop_back();
      return string{rbegin(s3), rend(s3)};
    };
    
    auto isValid = [](SV s) { return s.length() == 1 || s[0] != '0'; };
    
    function additive = [&](SV s1, SV s2, SV right) {
      if (!isValid(s1) || !isValid(s2)) return false;      
      string s3 = add(s1, s2);
      const int l3 = s3.length();
      if (right.substr(0, l3) != s3) return false;
      if (right.length() == l3) return true;
      return additive(s2, s3, right.substr(l3));
    };
    
    for (int i = 1; i <= s.size(); ++i)
      for (int j = 1; i + j <= s.size(); ++j)
        if (additive(s.substr(0, i), s.substr(i, j), s.substr(i + j))) 
          return true;
    return false;
  }
};

Python3

class Solution:
  def isAdditiveNumber(self, num: str) -> bool:
    n = len(num)
    
    def valid(s): return len(s) == 1 or s[0] != '0'
    
    def additive(s1, s2, right):
      if not valid(s1) or not valid(s2): return False
      s3 = str(int(s1) + int(s2))
      if right.startswith(s3):
        if right == s3: return True
        return additive(s2, s3, right[len(s3):])
      return False
      
    for l1 in range(1, n // 2 + 1):
      for l2 in range(1, n + 1 - l1):
        if additive(num[:l1], num[l1:l1+l2], num[l1+l2:]):
          return True
    return False

The post 花花酱 LeetCode 306. Additive Number appeared first on Huahua's Tech Road.

花花酱 LeetCode 989. Add to Array-Form of Integer

zxi — Sun, 10 Feb 2019 09:12:20 +0000

For a non-negative integer X, the array-form of X is an array of its digits in left to right order. For example, if X = 1231, then the array form is [1,2,3,1].

Given the array-form A of a non-negative integer X, return the array-form of the integer X+K.

Example 1:

Input: A = [1,2,0,0], K = 34
Output: [1,2,3,4]
Explanation: 1200 + 34 = 1234

Example 2:

Input: A = [2,7,4], K = 181
Output: [4,5,5]
Explanation: 274 + 181 = 455

Example 3:

Input: A = [2,1,5], K = 806
Output: [1,0,2,1]
Explanation: 215 + 806 = 1021

Example 4:

Input: A = [9,9,9,9,9,9,9,9,9,9], K = 1
Output: [1,0,0,0,0,0,0,0,0,0,0]
Explanation: 9999999999 + 1 = 10000000000

Note：

1 <= A.length <= 10000
0 <= A[i] <= 9
0 <= K <= 10000
If A.length > 1, then A[0] != 0

Solution: Simulation

Time complexity: O(n) Space complexity: O(n)

C++

// Author: Huahua, running time: 136 ms, 10.1 MB
class Solution {
public:
  vector addToArrayForm(vector& A, int K) {
    vector ans;
    ans.reserve(A.size() + 1);    
    for (int i = A.size() - 1; i >= 0 || K > 0; --i) {
      K += (i >= 0 ? A[i] : 0);
      ans.push_back(K % 10);
      K /= 10;
    }    
    reverse(begin(ans), end(ans));
    return ans;
  }
};

The post 花花酱 LeetCode 989. Add to Array-Form of Integer appeared first on Huahua's Tech Road.

high precision Archives - Huahua's Tech Road

花花酱 LeetCode 306. Additive Number

Solution: DFS

C++

Python3

花花酱 LeetCode 989. Add to Array-Form of Integer

Solution: Simulation

C++