题意
题解
方法一：暴力方法
枚举宽度或者高度
方法二：单调栈
import java.util.ArrayDeque;
import java.util.Deque;
public class Solution {
public int largestRectangleArea(int[] heights) {
int len = heights.length;
if (len == 0) {
return 0;
}
if (len == 1) {
return heights[0];
}
int area = 0;
Deque<Integer> stack = new ArrayDeque<>();
for (int i = 0; i < len; i++) {
while (!stack.isEmpty() && heights[stack.peekLast()] > heights[i]){
int height = heights[stack.removeLast()];
while (!stack.isEmpty() && heights[stack.peekLast()] == height){
stack.removeLast();
}
int width;
if (stack.isEmpty()){
width = i;
} else {
width = i - stack.peekLast() - 1;
}
area = Math.max(area , width * height);
}
stack.addLast(i);
}
while (!stack.isEmpty()){
int height = heights[stack.removeLast()];
while (!stack.isEmpty() && heights[stack.peekLast()] == height){
stack.removeLast();
}
int width;
if (stack.isEmpty()){
width = len;
} else {
width = len - stack.peekLast() - 1;
}
area = Math.max(area , width * height);
}
return area;
}
}
方法三：单调栈+哨兵
import java.util.ArrayDeque;
import java.util.Deque;
public class Solution {
public int largestRectangleArea(int[] heights) {
int len = heights.length;
if (len == 0) {
return 0;
}
if (len == 1) {
return heights[0];
}
int area = 0;
int[] newHeights = new int[len + 2];
for (int i = 0; i < len; i++) {
newHeights[i + 1] = heights[i];
}
len += 2;
heights = newHeights;
Deque<Integer> stack = new ArrayDeque<>();
stack.addLast(0);
for (int i = 1; i < len; i++) {
while (heights[stack.peekLast()] > heights[i]) {
int height = heights[stack.removeLast()];
int width = i - stack.peekLast() - 1;
area = Math.max(area, width * height);
}
stack.addLast(i);
}
return area;
}
}