题目描述

Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. The algorithm should run in linear time and in O(1) space.

分析

因为题目中说是大于⌊ n/3 ⌋次数的元素，这样的元素最多只能有2个。

参考：LeetCode 169 Majority Element

代码

    public static List<Integer> majorityElement(int[] nums) { List<Integer> rt = new ArrayList<Integer>(); if (nums == null || nums.length == 0) { return rt; }

        int m1 = nums[0];
        int m2 = 0;

        int c1 = 1;
        int c2 = 0;

        for (int i = 1; i < nums.length; i++) { int x = nums[i]; if (x == m1) { c1++; } else if (x == m2) { c2++; } else if (c1 == 0) { m1 = x; c1 = 1; } else if (c2 == 0) { m2 = x; c2 = 1; } else { c1--; c2--; }
        }

        c1 = 0;
        c2 = 0;

        for (int i = 0; i < nums.length; i++) { if (m1 == nums[i]) { c1++; } else if (m2 == nums[i]) { c2++; }
        }

        if (c1 > nums.length / 3) { rt.add(m1); }

        if (c2 > nums.length / 3) { rt.add(m2); }

        return rt;
    }