LeetCode: Largest Rectangle in Histogram

没想出来，看了网上答案再改了改

class Solution {
public:
    struct node {
        int left;
        int right;
    };
    int largestRectangleArea(vector<int> &height) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int n = height.size();
        vector<struct node> record(n);
        for (int i = 0; i < n; i++) {
            record[i].left = i;
            while (record[i].left > 0 && height[i] <= height[record[i].left-1])
                record[i].left = record[record[i].left-1].left;            
        }
        for (int i = n-1; i >= 0; i--) {
            record[i].right = i;
            while (record[i].right < n-1 && height[i] <= height[record[i].right+1])
                record[i].right = record[record[i].right+1].right;
        }
        int largest = 0;
        for (int i = 0; i < n; i++)
            largest = max(largest, height[i] * (record[i].right - record[i].left + 1));
        return largest;
    }
};

 再贴段容易理解的代码

class Solution {
public:
    int largestRectangleArea(vector<int> &h) {
        stack<int> S;
        h.push_back(0);
        int sum = 0;
        for (int i = 0; i < h.size(); i++) {
            if (S.empty() || h[i] > h[S.top()]) S.push(i);
            else {
                int tmp = S.top();
                S.pop();
                sum = max(sum, h[tmp]*(S.empty()? i : i-S.top()-1));
                i--;
            }
        }
        return sum;
    }
};

 C#

public class Solution {
    public int LargestRectangleArea(int[] height) {
        Stack<int> S = new Stack<int>();
        int[] heights = new int[height.Length+1];
        int sum = 0;
        Array.Copy(height, heights, height.Length);
        for (int i = 0; i < heights.Length; i++) {
            if (S.Count == 0 || heights[i] > heights[S.Peek()]) S.Push(i);
            else {
                int peek = S.Peek();
                S.Pop();
                sum = Math.Max(sum, heights[peek]*(S.Count == 0? i : i-S.Peek()-1));
                i--;
            }
        }
        return sum;
    }
}