代码随想录算法训练营第44天 | 第十章 单调栈part02

文章目录

• 今日记录
• [42. 接雨水](#42. 接雨水)
• 84.柱状图中最大的矩形
• 总结

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今日记录

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42. 接雨水

Leetcode链接

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

84.柱状图中最大的矩形

class Solution {
public:
    int largestRectangleArea(vector<int>& heights) {
        int result = 0;
        stack<int> st;
        st.push(0);
        heights.insert(heights.begin(), 0);
        heights.push_back(0);

        for (int i = 1; i < heights.size(); i++) {
            if (heights[i] > heights[st.top()]) {
                st.push(i);
            } else if (heights[i] == heights[st.top()]) {
                st.pop();
                st.push(i);
            } else {
                while (!st.empty() && heights[i] < heights[st.top()]) {
                    int mid = st.top();
                    st.pop();
                    int left = st.top();
                    int right = i;
                    int w = right - left - 1;
                    int h = heights[mid];
                    result = max(result, w * h);
                }
            }
            st.push(i);
        }
        return result;
    }
};

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总结