代码随想录Day59 | 503.下一个更大元素II 、42. 接雨水

503.下一个更大元素II

方法一：直接拼一个原数组在后面，模拟成环的过程

方法二：取模i%nums.size(), 循环到两倍数组长度\

class Solution {
public:
    vector nextGreaterElements(vector& nums) {
        vector result(nums.size(), -1);
        if (nums.size() == 0) return result;
        stack 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 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

按列计算

第一个和最后一根柱不接雨水

class Solution {
public:
    int trap(vector& height) {
        int sum = 0;
        for (int i = 0; i < height.size(); i++) {
            if (i == 0 || i == height.size() - 1) continue;
            int rHeight = height[i];
            int lHeight = height[i];
            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;
    }
};