🌕 414. 第三大的数

难度: 🌕

问题描述

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解法

class Solution {
    public int thirdMax(int[] nums) {
        // 思路：
        // 遍历，确定 first, second, third 变量
        int len = nums.length;
        if(len < 3) {
            int res = nums[0];
            for(int i = 1; i < len; i ++) {
                res = Math.max(res, nums[i]);
            }
            return res;
        }
        // len >= 3
        Integer first = nums[0]; // 运用 包装类 可以判断变量是否已经被赋值
        Integer second = null;
        Integer third = null;
        for(int i = 0; i < len; i ++) {
            if(first == null || nums[i] > first) {
                // 整体后移
                third = second;
                second = first;
                first = nums[i];
            } else if(nums[i] < first && (second == null || nums[i] > second)) {
                third = second;
                second = nums[i];
            } else if((second != null && nums[i] < second) && (third == null || nums[i] > third)) {
                third = nums[i];
            } 
        }
        return (third == null) ? first: third;
    }
}

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输出