numDecodings DB问题

var numDecodings = function(s) {
   if (s.length === 0) return 0;

      const N = s.length;
      const dp = Array(N+1).fill(0);

      dp[0] = 1;
      dp[1] = s[0] === '0' ? 0 : 1;

      for (let i = 2; i <= N; i++) {
        if (s[i-1] !== '0') {
          console.log(i,dp[i],dp[i-1])
          dp[i] = dp[i] + dp[i-1];
        }
        if (s[i-2] === '1' || s[i-2] === '2' && s[i-1] <= '6') {
          dp[i] = dp[i] + dp[i-2];
        }
      }

      return dp[N];
};