feat: add solutions to lc problem: No.0739

No.0739.Daily Temperatures

Author: yanglbme

solution/0700-0799/0739.Daily Temperatures/README.md

@@ -59,21 +59,13 @@ tags:
 
 ### 方法一：单调栈
 
-单调栈常见模型：找出每个数左/右边**离它最近的**且**比它大/小的数**。模板：
+本题需要我们找出每个元素右边第一个比它大的元素的位置，这是一个典型的单调栈应用场景。
 
-```python
-stk = []
-for i in range(n):
-    while stk and check(stk[-1], i):
-        stk.pop()
-    stk.append(i)
-```
+我们从右往左遍历数组 $\textit{temperatures}$，维护一个从栈顶到栈底温度单调递增的栈 $\textit{stk}$，栈中存储的是数组元素的下标。对于每个元素 $\textit{temperatures}[i]$，我们不断将其与栈顶元素进行比较，如果栈顶元素对应的温度小于等于 $\textit{temperatures}[i]$，那么循环将栈顶元素弹出，直到栈为空或者栈顶元素对应的温度大于 $\textit{temperatures}[i]$。此时，栈顶元素就是右边第一个比 $\textit{temperatures}[i]$ 大的元素，距离为 $\textit{stk.top()} - i$，我们更新答案数组。然后将 $\textit{temperatures}[i]$ 入栈，继续遍历。
 
-对于本题，我们需要找出每个数右边**离它最近的**且**比它大的数**，因此我们可以从右往左遍历数组，且需要维护一个从栈底到栈顶单调递减的栈。
+遍历结束后，返回答案数组即可。
 
-对于当前遍历到的数 `temperatures[i]`，如果栈顶元素 `temperatures[stk[-1]]` 小于等于 `temperatures[i]`，则弹出栈顶元素，直到栈为空或者栈顶元素大于 `temperatures[i]`。如果此时栈不为空，那么栈顶元素就是 `temperatures[i]` 右边离它最近的且比它大的数，更新 `ans[i] = stk[-1] - i`。接着，我们将 $i$ 入栈，继续遍历下一个数。
-
-时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 为 `temperatures` 数组的长度。
+时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 为数组 $\textit{temperatures}$ 的长度。
 
 <!-- tabs:start -->
 
@@ -82,12 +74,14 @@ for i in range(n):
 ```python
 class Solution:
     def dailyTemperatures(self, temperatures: List[int]) -> List[int]:
-        ans = [0] * len(temperatures)
         stk = []
-        for i, t in enumerate(temperatures):
-            while stk and temperatures[stk[-1]] < t:
-                j = stk.pop()
-                ans[j] = i - j
+        n = len(temperatures)
+        ans = [0] * n
+        for i in range(n - 1, -1, -1):
+            while stk and temperatures[stk[-1]] <= temperatures[i]:
+                stk.pop()
+            if stk:
+                ans[i] = stk[-1] - i
             stk.append(i)
         return ans
 ```
@@ -98,12 +92,14 @@ class Solution:
 class Solution {
     public int[] dailyTemperatures(int[] temperatures) {
         int n = temperatures.length;
-        int[] ans = new int[n];
         Deque<Integer> stk = new ArrayDeque<>();
-        for (int i = 0; i < n; ++i) {
-            while (!stk.isEmpty() && temperatures[stk.peek()] < temperatures[i]) {
-                int j = stk.pop();
-                ans[j] = i - j;
+        int[] ans = new int[n];
+        for (int i = n - 1; i >= 0; --i) {
+            while (!stk.isEmpty() && temperatures[stk.peek()] <= temperatures[i]) {
+                stk.pop();
+            }
+            if (!stk.isEmpty()) {
+                ans[i] = stk.peek() - i;
             }
             stk.push(i);
         }
@@ -119,13 +115,15 @@ class Solution {
 public:
     vector<int> dailyTemperatures(vector<int>& temperatures) {
         int n = temperatures.size();
-        vector<int> ans(n);
         stack<int> stk;
-        for (int i = 0; i < n; ++i) {
-            while (!stk.empty() && temperatures[stk.top()] < temperatures[i]) {
-                ans[stk.top()] = i - stk.top();
+        vector<int> ans(n);
+        for (int i = n - 1; ~i; --i) {
+            while (!stk.empty() && temperatures[stk.top()] <= temperatures[i]) {
                 stk.pop();
             }
+            if (!stk.empty()) {
+                ans[i] = stk.top() - i;
+            }
             stk.push(i);
         }
         return ans;
@@ -137,14 +135,16 @@ public:
 
 ```go
 func dailyTemperatures(temperatures []int) []int {
-	ans := make([]int, len(temperatures))
-	var stk []int
-	for i, t := range temperatures {
-		for len(stk) > 0 && temperatures[stk[len(stk)-1]] < t {
-			j := stk[len(stk)-1]
-			ans[j] = i - j
+	n := len(temperatures)
+	ans := make([]int, n)
+	stk := []int{}
+	for i := n - 1; i >= 0; i-- {
+		for len(stk) > 0 && temperatures[stk[len(stk)-1]] <= temperatures[i] {
 			stk = stk[:len(stk)-1]
 		}
+		if len(stk) > 0 {
+			ans[i] = stk[len(stk)-1] - i
+		}
 		stk = append(stk, i)
 	}
 	return ans
@@ -156,14 +156,14 @@ func dailyTemperatures(temperatures []int) []int {
 ```ts
 function dailyTemperatures(temperatures: number[]): number[] {
     const n = temperatures.length;
-    const ans = new Array(n).fill(0);
+    const ans: number[] = Array(n).fill(0);
     const stk: number[] = [];
-    for (let i = n - 1; i >= 0; --i) {
-        while (stk.length && temperatures[stk[stk.length - 1]] <= temperatures[i]) {
+    for (let i = n - 1; ~i; --i) {
+        while (stk.length && temperatures[stk.at(-1)!] <= temperatures[i]) {
             stk.pop();
         }
         if (stk.length) {
-            ans[i] = stk[stk.length - 1] - i;
+            ans[i] = stk.at(-1)! - i;
         }
         stk.push(i);
     }
@@ -191,6 +191,34 @@ impl Solution {
 }
 ```
 
+#### Rust
+
+```rust
+impl Solution {
+    pub fn daily_temperatures(temperatures: Vec<i32>) -> Vec<i32> {
+        let n = temperatures.len();
+        let mut stk: Vec<usize> = Vec::new();
+        let mut ans = vec![0; n];
+
+        for i in (0..n).rev() {
+            while let Some(&top) = stk.last() {
+                if temperatures[top] <= temperatures[i] {
+                    stk.pop();
+                } else {
+                    break;
+                }
+            }
+            if let Some(&top) = stk.last() {
+                ans[i] = (top - i) as i32;
+            }
+            stk.push(i);
+        }
+
+        ans
+    }
+}
+```
+
 #### JavaScript
 
 ```js
@@ -200,14 +228,14 @@ impl Solution {
  */
 var dailyTemperatures = function (temperatures) {
     const n = temperatures.length;
-    const ans = new Array(n).fill(0);
+    const ans = Array(n).fill(0);
     const stk = [];
-    for (let i = n - 1; i >= 0; --i) {
-        while (stk.length && temperatures[stk[stk.length - 1]] <= temperatures[i]) {
+    for (let i = n - 1; ~i; --i) {
+        while (stk.length && temperatures[stk.at(-1)] <= temperatures[i]) {
             stk.pop();
         }
         if (stk.length) {
-            ans[i] = stk[stk.length - 1] - i;
+            ans[i] = stk.at(-1) - i;
         }
         stk.push(i);
     }
@@ -219,92 +247,4 @@ var dailyTemperatures = function (temperatures) {
 
 <!-- solution:end -->
 
-<!-- solution:start -->
-
-### 方法二
-
-<!-- tabs:start -->
-
-#### Python3
-
-```python
-class Solution:
-    def dailyTemperatures(self, temperatures: List[int]) -> List[int]:
-        n = len(temperatures)
-        stk = []
-        ans = [0] * n
-        for i in range(n - 1, -1, -1):
-            while stk and temperatures[stk[-1]] <= temperatures[i]:
-                stk.pop()
-            if stk:
-                ans[i] = stk[-1] - i
-            stk.append(i)
-        return ans
-```
-
-#### Java
-
-```java
-class Solution {
-    public int[] dailyTemperatures(int[] temperatures) {
-        int n = temperatures.length;
-        Deque<Integer> stk = new ArrayDeque<>();
-        int[] ans = new int[n];
-        for (int i = n - 1; i >= 0; --i) {
-            while (!stk.isEmpty() && temperatures[stk.peek()] <= temperatures[i]) {
-                stk.pop();
-            }
-            if (!stk.isEmpty()) {
-                ans[i] = stk.peek() - i;
-            }
-            stk.push(i);
-        }
-        return ans;
-    }
-}
-```
-
-#### C++
-
-```cpp
-class Solution {
-public:
-    vector<int> dailyTemperatures(vector<int>& temperatures) {
-        int n = temperatures.size();
-        vector<int> ans(n);
-        stack<int> stk;
-        for (int i = n - 1; ~i; --i) {
-            while (!stk.empty() && temperatures[stk.top()] <= temperatures[i]) stk.pop();
-            if (!stk.empty()) ans[i] = stk.top() - i;
-            stk.push(i);
-        }
-        return ans;
-    }
-};
-```
-
-#### Go
-
-```go
-func dailyTemperatures(temperatures []int) []int {
-	n := len(temperatures)
-	ans := make([]int, n)
-	var stk []int
-	for i := n - 1; i >= 0; i-- {
-		for len(stk) > 0 && temperatures[stk[len(stk)-1]] <= temperatures[i] {
-			stk = stk[:len(stk)-1]
-		}
-		if len(stk) > 0 {
-			ans[i] = stk[len(stk)-1] - i
-		}
-		stk = append(stk, i)
-	}
-	return ans
-}
-```
-
-<!-- tabs:end -->
-
-<!-- solution:end -->
-
 <!-- problem:end -->