add test 9 13 14

chenweijie · chenweijie · commit 2e22d7629aa1 · 2019-09-05T01:06:01.000+08:00
diff --git a/src/main/java/com/chen/algorithm/study/test13/Solution.java b/src/main/java/com/chen/algorithm/study/test13/Solution.java
@@ -0,0 +1,81 @@
+package com.chen.algorithm.study.test13;
+
+import org.junit.Test;
+
+/**
+ * @author :  chen weijie
+ * @Date: 2019-09-04 23:18
+ */
+public class Solution {
+
+
+    public int romanToInt(String s) {
+
+        if (s == null || "".equals(s)) {
+            return 0;
+        }
+
+        char[] chars = s.toCharArray();
+        Integer[] integers = new Integer[chars.length];
+
+        for (int i = 0; i < chars.length; i++) {
+
+            switch (chars[i]) {
+                case 'I':
+                    integers[i] = 1;
+                    continue;
+                case 'V':
+                    integers[i] = 5;
+                    continue;
+                case 'X':
+                    integers[i] = 10;
+                    continue;
+                case 'L':
+                    integers[i] = 50;
+                    continue;
+                case 'C':
+                    integers[i] = 100;
+                    continue;
+                case 'D':
+                    integers[i] = 500;
+                    continue;
+                case 'M':
+                    integers[i] = 1000;
+                    continue;
+                default:
+            }
+        }
+
+
+        int firstValue = 0;
+        int nextValue = 0;
+        int sum = 0;
+
+
+        for (int i = 0; i < integers.length; i++) {
+            firstValue = integers[i];
+
+            if (i == s.length() - 1) {
+                sum += firstValue;
+            } else {
+                nextValue = integers[i + 1];
+                if (firstValue >= nextValue) {
+                    sum += firstValue;
+                } else {
+                    sum -= firstValue;
+                }
+            }
+
+
+        }
+        return sum;
+    }
+
+
+    @Test
+    public void testCase() {
+        System.out.println(romanToInt("IV"));
+    }
+
+
+}
diff --git a/src/main/java/com/chen/algorithm/study/test14/Solution.java b/src/main/java/com/chen/algorithm/study/test14/Solution.java
@@ -0,0 +1,64 @@
+package com.chen.algorithm.study.test14;
+
+import org.junit.Test;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ *
+ * 错误
+ *
+ *
+ * @author :  chen weijie
+ * @Date: 2019-09-05 00:17
+ */
+public class Solution {
+
+
+    public String longestCommonPrefix(String[] strs) {
+
+        if (strs == null || strs.length == 0) {
+
+            return "";
+        }
+
+
+        String result;
+        Map<String, String> map = new HashMap<>();
+
+        loop:
+        for (int j = 0; ; j++) {
+            for (int i = 0; i < strs.length; i++) {
+                if (strs[i] == null || "".equals(strs[i])) {
+                    return "";
+                }
+
+                if (i == 0) {
+                    map.put(strs[i].substring(0, j), strs[i].substring(0, j));
+                    continue;
+                }
+                if (!map.containsKey(strs[i].substring(0, j))) {
+                    result = strs[i].substring(0, j - 1);
+                    break loop;
+                }
+            }
+        }
+        return result;
+
+    }
+
+    @Test
+    public void testCase(){
+
+
+        String [] strings = {""};
+
+        System.out.println(longestCommonPrefix(strings));
+
+
+
+    }
+
+
+}
diff --git a/src/main/java/com/chen/algorithm/study/test14/Solution2.java b/src/main/java/com/chen/algorithm/study/test14/Solution2.java
@@ -0,0 +1,47 @@
+package com.chen.algorithm.study.test14;
+
+import org.junit.Test;
+
+/**
+ * @author :  chen weijie
+ * @Date: 2019-09-05 00:55
+ */
+public class Solution2 {
+
+
+    public String longestCommonPrefix(String[] strs) {
+
+        if (strs.length == 0) {
+            return "";
+        }
+
+        String prefix = strs[0];
+        for (int i = 1; i < strs.length; i++) {
+            while (!strs[i].startsWith(prefix)) {
+                prefix = prefix.substring(0, prefix.length() - 1);
+                if (prefix.isEmpty()) {
+                    return "";
+                }
+            }
+        }
+        return prefix;
+    }
+
+
+    @Test
+    public void testCase(){
+
+
+        String [] strings = {"flower","flow","flight"};
+
+        System.out.println(longestCommonPrefix(strings));
+
+
+
+    }
+
+
+
+
+
+}
diff --git a/src/main/java/com/chen/algorithm/study/test9/Solution.java b/src/main/java/com/chen/algorithm/study/test9/Solution.java
@@ -0,0 +1,36 @@
+package com.chen.algorithm.study.test9;
+
+import org.junit.Test;
+
+/**
+ * @author :  chen weijie
+ * @Date: 2019-09-04 22:54
+ */
+public class Solution {
+
+
+    public boolean isPalindrome(int x) {
+
+        if (x < 0) {
+            return false;
+        }
+
+        char[] chars = String.valueOf(x).toCharArray();
+
+        StringBuilder sb = new StringBuilder();
+        for (int i = chars.length - 1; i >= 0; i--) {
+            sb.append(chars[i]);
+        }
+
+        return x == Long.parseLong(sb.toString());
+    }
+
+
+
+    @Test
+    public void testCase(){
+        System.out.println(isPalindrome(2147483647));
+    }
+
+
+}
diff --git a/src/main/java/com/chen/algorithm/study/test9/Solution2.java b/src/main/java/com/chen/algorithm/study/test9/Solution2.java
@@ -0,0 +1,45 @@
+package com.chen.algorithm.study.test9;
+
+import org.junit.Test;
+
+/**
+ * @author :  chen weijie
+ * @Date: 2019-09-04 23:09
+ */
+public class Solution2 {
+
+
+//    通过计算 1221 / 1000， 得首位1
+//    通过计算 1221 % 10， 可得末位 1
+
+    public boolean isPalindrome(int x) {
+        //边界判断
+        if (x < 0) {
+            return false;
+        }
+
+        int div = 1;
+        //
+        while (x / div >= 10) {
+            div *= 10;
+        }
+
+        while (x > 0) {
+            int left = x / div;
+            int right = x % 10;
+            if (left != right) {
+                return false;
+            }
+            x = (x % div) / 10;
+            div /= 100;
+        }
+        return true;
+    }
+
+
+    @Test
+    public void testCase() {
+        System.out.println(isPalindrome(121));
+    }
+
+}
