Sep 02, 2018 原创文章
Leetcode 91. Decode Ways
问题描述
A message containing letters from A-Z is being encoded to numbers using the following mapping:
‘A’ -> 1
‘B’ -> 2
…
‘Z’ -> 26
Given a non-empty string containing only digits, determine the total number of ways to decode it.
Example 1:
Input: “12”
Output: 2
Explanation: It could be decoded as “AB” (1 2) or “L” (12).
Example 2:
Input: “226”
Output: 3
Explanation: It could be decoded as “BZ” (2 26), “VF” (22 6), or “BBF” (2 2 6).
class Solution {
public:
int numDecodings(string s) {
if (s.empty() || '0' == s.front()) {
return 0;
}
vector <int> comb(1, 1);
for (int i = 0; i < s.size(); i++)
{
if (num % 10 == 0 ||num == 0)
{
if (num == 0 || num > 20)
{
return 0;
}
else
{
comb.push_back(comb[i - 1]);
}
}
else
{
if (num >= 10 && num <= 26 && num % 10 != 0&&s[i] != '0')
{
comb.push_back(comb[i - 1] + comb[i]);
}
else
{
comb.push_back(comb[i]);
}
}
}
return comb.back();
}};
