增加No5

Author: tujietg

String/No5.java

@@ -0,0 +1,39 @@
+/**
+ * @author tujietg
+ * @date 5/21/20 9:07 AM
+ */
+public class No5 {
+    public String longestPalindrome(String s) {
+        int len = s.length();
+        if (len < 2) {
+            return s;
+        }
+        int start = 0;
+        int midLen = 1;
+
+        boolean[][] bp = new boolean[len][len];
+        for (int i = 0; i < len; i++) {
+            bp[i][i] = true;
+        }
+
+        char[] charArr = s.toCharArray();
+        for (int j = 1; j < len; j++) {
+            for (int i = 0; i < j; i++) {
+                if (charArr[i] != charArr[j]) {
+                    bp[i][j] = false;
+                } else {
+                    if (j - i < 3) {
+                        bp[i][j] = true;
+                    } else {
+                        bp[i][j] = bp[i + 1][j - 1];
+                    }
+                }
+                if (bp[i][j] == true && j - i + 1 > midLen) {
+                    midLen = j - i + 1;
+                    start = i;
+                }
+            }
+        }
+        return s.substring(start, start + midLen);
+    }
+}