提交作业

ryuhi · ryuhi · commit 26e0728816a2 · 2020-08-10T01:56:39.000+08:00
diff --git a/Week09/FirstUniqChar.java b/Week09/FirstUniqChar.java
@@ -0,0 +1,22 @@
+public class FirstUniqChar {
+
+    public int firstUniqChar(String s) {
+        if (null == s || s.length() == 0) {
+            return -1;
+        }
+        int length = s.length();
+        int[] arr = new int[26];
+        char[] array = s.toCharArray();
+        for (char c : array) {
+            arr[c - 'a']++;
+        }
+
+        for (int i = 0; i < length; i++) {
+            if (arr[array[i] - 'a'] == 1) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+}
diff --git a/Week09/NOTE.md b/Week09/NOTE.md
@@ -1 +1,4 @@
-学习笔记
+学习笔记
+
+dp[i][j] = blocked ? 0 : dp[i−1,j]+dp[i,j−1]
+​
diff --git a/Week09/NumDecodings.java b/Week09/NumDecodings.java
@@ -0,0 +1,28 @@
+public class NumDecodings {
+
+    public int numDecodings(String s) {
+        if (s == null || s.length() == 0) {
+            return 0;
+        }
+        int len = s.length();
+        int[] dp = new int[len + 1];
+        dp[len] = 1;
+        if (s.charAt(len - 1) == '0') {
+            dp[len - 1] = 0;
+        } else {
+            dp[len - 1] = 1;
+        }
+        for (int i = len - 2; i >= 0; i--) {
+            if (s.charAt(i) == '0') {
+                dp[i] = 0;
+                continue;
+            }
+            if ((s.charAt(i) - '0') * 10 + (s.charAt(i + 1) - '0') <= 26) {
+                dp[i] = dp[i + 1] + dp[i + 2];
+            } else {
+                dp[i] = dp[i + 1];
+            }
+        }
+        return dp[0];
+    }
+}
