161. One Edit Distance

相隔为1 的编辑距离。

• 时间复杂度O(n)，空间复杂度O(1)
• Runtime: 84 ms, faster than 37.27%
• Memory Usage: 38.6 MB, less than 99.38%

/**
 * @param {string} s
 * @param {string} t
 * @return {boolean}
 */
var isOneEditDistance = function(s, t) {
  let sLen = s.length;
  let tLen = t.length;
  if (sLen > tLen) {
    return isOneEditDistance(t, s);
  }
  if (tLen - sLen > 1) {
    return false;
  }
  for (let i = 0; i < sLen; i++) {
    if (s[i] !== t[i]) {
      if (sLen === tLen) {
        return s.substring(i + 1) === t.substring(i + 1);
      } else {
        return s.substring(i) === t.substring(i + 1);
      }
    } 
  }
  return sLen + 1 === tLen;
};