lintcode 中 tle 错误，求大佬帮忙看下

题目: Strings Homomorphism

public class Solution { /** * @param s a string * @param t a string * @return true if the characters in s can be replaced to get t or false */ public boolean isIsomorphic(String s, String t) { // Write your code here if(s == null && t == null) return true; else if(s == null || t == null) return false; else if(s.length() != t.length()) return false; else{ String s1 = ""; String s2 = ""; int j = 0; for(int i = 0; i < s.length(); i++){ int dis1 = s.indexOf(s.charAt(i)); if(i == dis1){ s1 += j; j++; } else{ s1 += s1.charAt(dis1); } } int l = 0; for(int k = 0; k < t.length(); k++){ int dis2 = t.indexOf(t.charAt(k)); if(k == dis2){ s2 += l; l++; } else{ s2 += s2.charAt(dis2); } } boolean flag = s1.equals(s2); return flag; } } } 

还有另外一个 题目: First Position Unique Character

public class Solution { /* * @param s: a string * @return: it's index */ public int firstUniqChar(String s) { // write your code here if (s == null) { return -1; } boolean flag = false; int i = 0; for (; i < s.length() - 1; i++) { String myStr = s.substring(0, i) + s.substring(i + 1); String ch = Character.toString(s.charAt(i)); if (myStr.contains(ch)) { continue; } else { flag = true; break; } } if (flag) { return i; } else { return -1; } } }