solve : programmers 가장 긴 팰린드롬

do02reen24 · do02reen24 · commit f654f71732da · 2020-12-31T16:16:22.000+09:00
diff --git a/src/do02reen24/Review/week14.md b/src/do02reen24/Review/week14.md
@@ -78,3 +78,5 @@ const solution = (s) => {
   return maxLength;
 };
 ```
+
+- 처음 코드에서는 홀수 검사 결과가 있다면 짝수 검사를 진행하지 않았었는데, 짝수 검사의 결과가 더 큰 경우도 존재함을 알게 되었다. 따라서 두 경우를 모두 계산해주고 더 큰 값을 반환해주도록 변경하였다.
diff --git a/src/do02reen24/string/programmers_12904.js b/src/do02reen24/string/programmers_12904.js
@@ -0,0 +1,56 @@
+const isSameWord = (word, pre, next) => {
+  if (pre < 0 || next >= word.length) {
+    return false;
+  }
+  if (word[pre] !== word[next]) {
+    return false;
+  }
+  return true;
+};
+
+const oddPalindrome = (word, start) => {
+  let index = 1;
+  while (true) {
+    const pre = start - index;
+    const next = start + index;
+    if (isSameWord(word, pre, next)) {
+      index = index + 1;
+      continue;
+    }
+    index = index - 1;
+    break;
+  }
+  return index * 2 + 1;
+};
+
+const evenPalindrome = (word, start) => {
+  let index = 0;
+  while (true) {
+    const pre = start - index;
+    const next = start + 1 + index;
+    if (isSameWord(word, pre, next)) {
+      index = index + 1;
+      continue;
+    }
+    break;
+  }
+  return index * 2;
+};
+
+const isPalindrome = (word, start) => {
+  const oddResult = oddPalindrome(word, start);
+  const evenResult = evenPalindrome(word, start);
+  return Math.max(oddResult, evenResult);
+};
+
+const solution = (s) => {
+  let maxLength = 0;
+  for (let index = 0; index < s.length; index++) {
+    const result = isPalindrome(s, index);
+    if (maxLength < result) {
+      maxLength = result;
+    }
+  }
+
+  return maxLength;
+};
