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45 lines (38 loc) · 1.05 KB
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/*
91. Decode Ways (https://leetcode.com/problems/decode-ways)
Medium
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).
*/
package dp;
public class DecodeWays {
public static int decodeWaysS1(String s) {
int pre = 1;
int curr = s.charAt(0) == 0 ? 0 : 1;
for (int i = 1; i < s.length(); i++) {
int temp = curr;
if (s.charAt(i) == '0') {
pre = temp;
continue;
}
int now = Integer.parseInt(s.substring(i - 1, i + 1));
if (s.charAt(i - 1) != '0' && now <= 26) {
curr += pre;
}
pre = temp;
}
return curr;
}
}