Day59 单调栈part02 503. 下一个更大元素 II 42. 接雨水

503. 下一个更大元素 II

class Solution {
public:vector<int> nextGreaterElements(vector<int>& nums) {vector<int> result(nums.size(),-1); stack<int> st;st.push(0);for(int i = 1; i<nums.size()*2;i++){if(nums[i% nums.size()]<=nums[st.top()]) st.push(i% nums.size());else{while(!st.empty()&&nums[i% nums.size()]>nums[st.top()]){result[st.top()] = nums[i% nums.size()];st.pop();}st.push(i% nums.size());}}return result;}
};

42. 接雨水

暴力法

class Solution {
public:int trap(vector<int>& height) {int sum = 0;for (int i = 0; i < height.size(); i++) {int rHeight = height[i]; // 记录右边柱子的最高高度int lHeight = height[i]; // 记录左边柱子的最高高度for (int r = i + 1; r < height.size(); r++) {if (height[r] > rHeight) rHeight = height[r];}for (int l = i - 1; l >= 0; l--) {if (height[l] > lHeight) lHeight = height[l];}int h = min(lHeight, rHeight) - height[i];if (h > 0) sum += h;}return sum;}
};

单调栈

class Solution {
public:int trap(vector<int>& height) {int result =0;stack<int> stk;stk.push(0);for(int i = 1;i<height.size();i++){while(!stk.empty()&& height[i] > height[stk.top()]){int mid = stk.top();stk.pop();if(!stk.empty()){int h = min(height[stk.top()],height[i]) - height[mid];int w = i - stk.top() -1;result += h*w;}}stk.push(i);}return result;}
};