给定一长一短的两个字符串 A，B，假设 A 长 B 短，要判断 A 是否包含了 B 中所有的字母。《程序员编程艺术二》

【算】字母包含问题.js

window.myApp = (function (myApp) {
  
  // O(m+n)
  myApp.containChar = function (Str1, Str2) {
    
    if (typeof Str1 !== "string" || typeof Str2 !== "string") {
      return;
    }
    
    var longStr,
        shortStr,
        alphabet = {}, // 统计 shortStr 字母表
        alphaLen = 0,  // shortStr 字母类型个数
        count = 0,     // 匹配的字母的类型个数
        i, t;
    
    if (Str1.length > Str2.length) {
      longStr = Str1;
      shortStr = Str2;
    } else {
      longStr = Str2;
      shortStr = Str1;
    }
    
    for (i = 0; i < shortStr.length; i += 1) {
      t = shortStr.charAt(i);
      if (!alphabet.hasOwnProperty(t)) {
        alphabet[t] = true;
        alphaLen += 1;
      }
    }
    
    for (i = 0; i < longStr.length; i += 1) {
      t = longStr.charAt(i);
      if (alphabet.hasOwnProperty(t)) {
        if (alphabet[t] === true) {
          alphabet[t] = false;
          count += 1;
          // 把 shortStr 字母表所有类型的字母都匹配了，不用继续匹配
          if (count === alphaLen) {
            return true;
          }
        }
      } else {
        return false;
      }
    }
    return true;
    
  }; // end function containChar
  
  return myApp;
 
}(window.myApp || {}));
 
console.log(myApp.containChar("abcdefghijk", "abc"));  // true
console.log(myApp.containChar("abc", "abcdefghijk"));  // true
console.log(myApp.containChar("abcdefghijk", "zabc")); // false
console.log(myApp.containChar("abcdefghijk", ""));     // false