[LeetCode] Isomorphic Strings

Isomorphic Strings

Total Accepted: 30898 Total Submissions: 120944 Difficulty: Easy

Given two strings s and t, determine if they are isomorphic.

Two strings are isomorphic if the characters in s can be replaced to get t.

All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character but a character may map to itself.

For example,
Given "egg", "add", return true.

Given "foo", "bar", return false.

Given "paper", "title", return true.

Note:
You may assume both s and t have the same length.

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isIsomorphic = function(s, t) {
    var sp = 0;
    var tp = 0;

    var sm = {};
    var tm = {};

    if (s.length != t.length) return false;

    var st = "";
    for (var i = 0; i < s.length; i++) {
        if (sm[s[i]] == void 0) {
            sm[s[i]] = sp++;
        }
        st += sm[s[i]];
    }

    var tt = "";
    for (var i = 0; i < t.length; i++) {
        if (tm[t[i]] == void 0) {
            tm[t[i]] = tp++;
        }
        tt += tm[t[i]];
    }

    if (st == tt) return true;
    return false;
};

好像是word pattern 的姊妹题，这题是找pattern，所以比找match 要容易点。最简单的办法就是利用哈希表和一个递增的整数来把字符串归一化，如果归一化后的结果是一样的则是相同pattern 的字符串。javasscript 写起来方便但是要注意 !0 == true，所以改为判断和void 0 比较了。