Largest Rect in Histogram: stack, track last histogram that no lower than cur height.

Author: DeanChensj

Hard/084_Largest-Rectangle-in-Histogram.cpp

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+#include "../Header.h"
+
+using namespace std;
+int largestRectangleArea(vector<int>& heights) {
+    int maxArea = 0, sz = heights.size();
+    stack<int> lastIndex;
+    for (int i = 0; i < sz; i++) {
+        while (!lastIndex.empty() && heights[lastIndex.top()] > heights[i]) {
+            int l = lastIndex.top();
+            lastIndex.pop();
+            // w+1 代表的坐标是高度不小于当前高度的最左边的坐标
+            // 栈空代表当前高度为目前为止的最低高度
+            int w = lastIndex.empty() ? -1 : lastIndex.top();
+            maxArea = max(maxArea, heights[l] * (i - (w + 1)));
+        }
+        lastIndex.push(i);
+    }
+    // 处理递增数列
+    while (!lastIndex.empty()) {
+        int l = lastIndex.top();
+        lastIndex.pop();
+        int w = lastIndex.empty() ? -1 : lastIndex.top();
+        maxArea = max(maxArea, heights[l] * (sz - (w + 1)));
+    }
+    return maxArea;
+}
+int main(int argc, char const *argv[])
+{
+    vector<int> v = genRandVector(10, 10);
+	cout << "v = " << toString(v) << endl;
+    cout << "largestRectangleArea(v) = " << largestRectangleArea(v) << endl;
+	return 0;
+}