int numDecodings(string s) {

// Start typing your C/C++ solution below

// DO NOT write int main() function

int size = s.size();

if(size == 0)

return 0;

int dp[size + 1];

for(int i = 0; i <= size; ++i)

dp[i] = 0;

dp[0] = 1;

for(int i = 1; i <= size; ++i)

{

if(s[i-1] != '0')

dp[i] = dp[i-1];

if(i >= 2)

{

int num = 10*(s[i-2]-'0') + s[i-1] -'0';

if(num >= 10 && num <= 26)

dp[i] += dp[i-2];

}

}

for(int i = 1; i <= size; ++i)

{

if(dp[i] == 0)

return 0;

}

return dp[size];

}