休息日的思考与额外题——双指针、原地哈希day28

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前言

一个本硕双非的小菜鸡，备战24年秋招，计划二刷完卡子哥的刷题计划，加油！
二刷决定精刷了，于是参加了卡子哥的刷题班，训练营为期60天，我一定能坚持下去，迎来两个月后的脱变的，加油！
推荐一手卡子哥的刷题网站，感谢卡子哥。代码随想录

一、11. 盛最多水的容器

11. 盛最多水的容器
Note：双指针

class Solution {
public:int maxArea(vector<int>& height) {int leftIndex = 0, rightIndex = height.size() - 1;int res = 0;while (leftIndex < rightIndex) {int ans = min(height[leftIndex], height[rightIndex]) * (rightIndex - leftIndex);res = max(ans, res);if (height[leftIndex] <= height[rightIndex])leftIndex++;elserightIndex--;}return res;}
};

二、41. 缺失的第一个正数

41. 缺失的第一个正数
Note：神思想，利用-1原地哈希

class Solution {
public:int firstMissingPositive(vector<int>& nums) {int size = nums.size();if (find(nums.begin(), nums.end(), 1) == nums.end())return 1;for (int i = 0; i < size; i++) {if (nums[i] <= 0 || nums[i] > size)nums[i] = 1;}for (int i = 0; i < size; i++) {int num = abs(nums[i]) - 1;nums[num] = -abs(nums[num]);}for (int i = 0; i < size; i++) {if (nums[i] > 0)return i + 1;}return size + 1;}
};

三、42. 接雨水

42. 接雨水
Note：双指针

class Solution {
public:int trap(vector<int>& height) {int ans = 0;int left = 0, right = height.size() - 1;int leftMax = 0, rightMax = 0;while (left < right) {leftMax = max(leftMax, height[left]);rightMax = max(rightMax, height[right]);if (height[left] < height[right]) {ans += leftMax - height[left];++left;} else {ans += rightMax - height[right];--right;}}return ans;}
};

总结

hot前100的三道题