Update 0084.柱状图中最大的矩形.md

problems/0084.柱状图中最大的矩形.md

@@ -670,6 +670,61 @@ function largestRectangleArea(heights: number[]): number {
 ```
 
 
+Rust
+
+双指针预处理
+```rust
+
+impl Solution {
+    pub fn largest_rectangle_area(v: Vec<i32>) -> i32 {
+        let n = v.len();
+        let mut left_smaller_idx = vec![-1; n];
+        let mut right_smaller_idx = vec![n as i32; n];
+        for i in 1..n {
+            let mut mid = i as i32 - 1;
+            while mid >= 0 && v[mid as usize] >= v[i] {
+                mid = left_smaller_idx[mid as usize];
+            }
+            left_smaller_idx[i] = mid;
+        }
+        for i in (0..n-1).rev() {
+            let mut mid = i + 1;
+            while mid < n && v[mid] >= v[i] {
+                mid = right_smaller_idx[mid] as usize;
+            }
+            right_smaller_idx[i] = mid as i32;
+        }
+        let mut res = 0;
+        for (idx, &e) in v.iter().enumerate() {
+            res = res.max((right_smaller_idx[idx] - left_smaller_idx[idx] - 1) * e);
+        }
+        dbg!(res)
+    }
+}
+```
+
+单调栈
+```rust
+impl Solution {
+    pub fn largest_rectangle_area1(mut v: Vec<i32>) -> i32 {
+        v.insert(0, 0);  // 便于使第一个元素能够有左侧<=它的值
+        v.push(0);                      // 便于在结束处理最后一个元素后清空残留在栈中的值
+        let mut res = 0;
+        let mut stack = vec![]; // 递增的栈
+        for (idx, &e) in v.iter().enumerate() {
+            while !stack.is_empty() && v[*stack.last().unwrap()] > e {
+                let pos = stack.pop().unwrap();
+                let prev_pos = *stack.last().unwrap();
+                let s = (idx - prev_pos - 1) as i32 * v[pos];
+                res = res.max(s);
+            }
+            stack.push(idx);
+        }
+        res
+    }  
+}
+```
+
 
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