LeetCode – Refresh – Largest Rectangle in Histogram

Use two vector to record left and right indexes that can extend the blocks.

 

class Solution {
public:
    int largestRectangleArea(vector<int> &height) {
        int len = height.size(), result = 0;
        vector<int> left(len), right(len);
        for (int i = 0; i < len; i++) {
            left[i] = i;
            while (left[i] > 0 && height[i] <= height[left[i]-1]) left[i] = left[left[i]-1];
        }
        for (int i = len-1; i >= 0; i--) {
            right[i] = i;
            while (right[i] < len-1 && height[i] <= height[right[i]+1]) right[i] = right[right[i]+1];
        }
        for (int i = 0; i < len; i++) {
            result = max(result, height[i] * (right[i] - left[i] + 1));
        }
        return result;
    }
};