标签：bsp highlight must class input first long isa seq
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, 190.
1 + 99 = 100, 99 + 100 = 199
Approach #1:
class Solution {
public:
bool isAdditiveNumber(string num) {
if (num.length() < 3) return false;
// if (num == "000") return true;
// cout <<"num.length() = " << num.length() << endl;
for (int i = 1; i <= num.length() / 2; ++i) { // the first number‘s length;
if (num[0] == ‘0‘ && i > 1) return false;
string s_first = num.substr(0, i);
long first = stol(s_first);
// cout << "first = " << s_first << endl;
for (int j = 1; num.length()-i-j >= max(i, j); ++j) {
string s_second = num.substr(i, j);
if (j > 1 && s_second[0] == ‘0‘) break;
long second = stol(s_second);
// cout << "second = " << s_second << endl;
if (isValid(first, second, i+j, num)) {
return true;
}
}
}
return false;
}
private:
bool isValid(long first, long second, int start, string num) {
// cout << "start = " << start << endl;
// cout << first << ‘ ‘ << second << endl;
if (start == num.length()) return true;
second = second + first;
first = second - first;
// cout << first << ‘ ‘ << second << endl;
string sum = to_string(second);
// cout << "sum = " << sum << endl;
return C_startWith(sum, start, num) && isValid(first, second, start+sum.length(), num);
}
bool C_startWith(string sum, int start, string num) {
int len = sum.length();
string temp = num.substr(start, len);
return temp == sum;
}
};
标签：bsp highlight must class input first long isa seq
原文地址：https://www.cnblogs.com/ruruozhenhao/p/10357028.html
