出现次数最多的字符

javascript面试题
javascript
  1. 问题：给定一个字符串，求出里面出现次数最多的字符。
  2. 输入：字符串
  3. 输出：{[字符]:[出现次数],…}
  4. 举例：输入：'hello world' 输出：{'l':3}

方法1:

先排序，然后单次遍历

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function getMostAppear(str){
	if(str.length === 0) return {};
	var sortedArr = str.split('').sort(function(a, b){
		return a - b;
	});
	var len = sortedArr.length;
	
	// 用来记录最多的次数
	var max = 0;
	
	// 用来记录出现最多次数的字符
	var c = '';
	
	// 用来记录当前字符和次数的映射
	var currAppear = {};
	for(var i = 0; i < len; i++){
		var currChar = sortedArr[i];
		if(!currAppear[currChar]){
			currAppear[currChar] = 1;
		}else{
			currAppear[currChar]++;
		}
		if(currAppear[currChar] > max){
			max = currAppear[currChar];
			c = currChar;
		}
	}
	var mostAppear = {};
	mostAppear[c] = max;
	return mostAppear;
}

方法2:

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function getMostAppear(str){
	if(str.length === 0) return {};
	var len = str.length;
	
	// 用来记录最多的次数
	var max = 0;
	
	// 用来记录出现最多次数的字符
	var c = '';
	
	// 字符和出现次数的映射
	var charNumMap = {};
	
	for(var i = 0; i < len; i++){
		var curr = str.charAt(i);
		if(!charNumMap[curr]){
			charNumMap[curr] = 1;
		}else{
			charNumMap[curr]++;
		}
		
		if(charNumMap[curr] > max){
			max = charNumMap[curr];
			c = curr;
		}
	}
	
	var mostAppear = {};
	mostAppear[c] = max;
	return mostAppear;
}
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