leetcode-5 longest palindromic substring

1.说明：

最长回文串，考虑到长度为奇数的回文串和长度为偶数的回文串。

2.代码：

var longestPalindrome = function(s) {    var max = 0;    var mark = {        i: 0,        j: 0    };    var result = '';    var getOddLength = function (s, index) {        var i = index;        var j = index;        while (i >= 0 && j < s.length) {            if (s[i] === s[j]) {                i--;                j++;            }            else {                break;            }        }        return j - i + 1;    };    var getEvenLength = function (s, index) {        if (index >= s.length ) {            return 0;        }        var i = index;        var j = index + 1;        while (i >= 0 && j < s.length) {            if (s[i] === s[j]) {                i--;                j++;            }            else {                break;            }        }        return j - i + 1;    };    var getResult = function (mark, s) {        var i = mark.i;        var j = mark.j;        var str = '';        while (i >= 0 && j < s.length) {            if (s[i] === s[j]) {                str = s[i] + str;                if (i !== j) {                    str = str + s[j];                }                i--;                j++;            }            else {                break;            }        }        return str;    };    for (var i = 0; i < s.length; i++) {        var l1 = getOddLength(s, i);        var l2 = getEvenLength(s, i);        if (l1 > max) {            max = l1;            mark.i = i;            mark.j = i;        }        if (l2 > max) {            max = l2;            mark.i = i;            mark.j = i + 1;        }    }    return getResult(mark, s);};