Leetcode:169. Majority Element(找到数组中出现次数最多的元素)

Given an array of size n, find the majority element. The majority element is the element that appears more than ⌊ n/2 ⌋ times.

You may assume that the array is non-empty and the majority element always exist in the array.

分析:拿到这题,很有可能会理解出错,那就是找出数组里面出现次数超过n/2次的,而不是找出出现次数最多的。
一开始我就理解错了题意。
基于这个,借助java封装的函数可写出下面简洁代码:

Method1:

    public int majorityElement(int[] nums) {
        Arrays.sort(nums);
        return nums[nums.length/2];
    }

Method2

这是我看别人写的,感觉这个方法很完美。

    public int majorityElement(int[] num) {

        int major=num[0], count = 1;
        for(int i=1; iif(count==0){
                count++;
                major=num[i];
            }else if(major==num[i]){
                count++;
            }else count--;

        }
        return major;
    }

Method3

Disscuss里面的答案:感觉这个蛮符合逻辑 比较容易想到。

// Hashtable 
public int majorityElement2(int[] nums) {
    Map myMap = new HashMap();
    //Hashtable myMap = new Hashtable();
    int ret=0;
    for (int num: nums) {
        if (!myMap.containsKey(num))
            myMap.put(num, 1);
        else
            myMap.put(num, myMap.get(num)+1);
        if (myMap.get(num)>nums.length/2) {
            ret = num;
            break;
        }
    }
    return ret;
}

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