【面试经典150】day 6

又到算法。

1.多数元素

class Solution {public int majorityElement(int[] nums) {//sort一下，返回nums[n/2]即可int n=nums.length;Arrays.sort(nums);return nums[n/2];}
}

 2.轮转数组

class Solution {public void rotate(int[] nums, int k) {int n=nums.length;k%=n;//这里是左闭右闭的reverse(nums,0,n-1);reverse(nums,0,k-1);reverse(nums,k,n-1);}private void reverse(int [] nums,int i,int j){while(i<j){//交换，相遇就不用交换了int tmp=nums[i];nums[i++]=nums[j];nums[j--]=tmp;}}
}

3.买卖股票的最佳时机

class Solution {public int maxProfit(int[] prices) {int cost = Integer.MAX_VALUE;int profit = 0;for (int price : prices) {cost = Math.min(cost, price);profit = Math.max(profit, price - cost);}return profit;}
}