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package class25;
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import java.util.Stack;
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// 测试链接：https://leetcode.com/problems/largest-rectangle-in-histogram
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public class Code03_LargestRectangleInHistogram {
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public static int largestRectangleArea1(int[] height) {
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if (height == null || height.length == 0) {
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return 0;
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}
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int maxArea = 0;
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Stack<Integer> stack = new Stack<Integer>();
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for (int i = 0; i < height.length; i++) {
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while (!stack.isEmpty() && height[i] <= height[stack.peek()]) {
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int j = stack.pop();
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int k = stack.isEmpty() ? -1 : stack.peek();
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int curArea = (i - k - 1) * height[j];
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maxArea = Math.max(maxArea, curArea);
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}
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stack.push(i);
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}
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while (!stack.isEmpty()) {
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int j = stack.pop();
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int k = stack.isEmpty() ? -1 : stack.peek();
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int curArea = (height.length - k - 1) * height[j];
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maxArea = Math.max(maxArea, curArea);
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}
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return maxArea;
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}
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public static int largestRectangleArea2(int[] height) {
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if (height == null || height.length == 0) {
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return 0;
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}
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int N = height.length;
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int[] stack = new int[N];
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int si = -1;
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int maxArea = 0;
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for (int i = 0; i < height.length; i++) {
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while (si != -1 && height[i] <= height[stack[si]]) {
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int j = stack[si--];
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int k = si == -1 ? -1 : stack[si];
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int curArea = (i - k - 1) * height[j];
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maxArea = Math.max(maxArea, curArea);
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}
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stack[++si] = i;
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}
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while (si != -1) {
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int j = stack[si--];
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int k = si == -1 ? -1 : stack[si];
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int curArea = (height.length - k - 1) * height[j];
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maxArea = Math.max(maxArea, curArea);
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}
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return maxArea;
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}
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}
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