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LeetCode_DecodeWays.cpp
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LeetCode_DecodeWays.cpp
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class Solution {
public:
int numDecodings(string s) {
int n = s.length();
vector<int> memo(n+1, 0);
memo[n] = 1;
for(int i = n-1; i >= 0; i--)
{
if(s[i] == '0')
{
memo[i] = 0;
}
else if(s[i] == '1')
{
if(i == n-1)
{
memo[i] = memo[i+1];
}
else
{
memo[i] = memo[i+1] + memo[i+2];
}
}
else if(s[i] == '2')
{
if(s[i+1] >= '0' && s[i+1] <= '6')
{
if(i == n-1)
{
memo[i] = memo[i+1];
}
else
{
memo[i] = memo[i+1] + memo[i+2];
}
}
else
{
memo[i] = memo[i+1];
}
}
else
{
memo[i] = memo[i+1];
}
}
return memo[0];
}
};