leetcode

Author: ayoubzulfiqar

DailyTemperatures/daily_temperatures.dart

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+/*
+
+- 739. Daily Temperatures -*
+
+
+Given an array of integers temperatures represents the daily temperatures, return an array answer such that answer[i] is the number of days you have to wait after the ith day to get a warmer temperature. If there is no future day for which this is possible, keep answer[i] == 0 instead.
+
+ 
+
+Example 1:
+
+Input: temperatures = [73,74,75,71,69,72,76,73]
+Output: [1,1,4,2,1,1,0,0]
+Example 2:
+
+Input: temperatures = [30,40,50,60]
+Output: [1,1,1,0]
+Example 3:
+
+Input: temperatures = [30,60,90]
+Output: [1,1,0]
+ 
+
+Constraints:
+
+1 <= temperatures.length <= 105
+30 <= temperatures[i] <= 100
+
+*/
+
+/*
+
+
+
+*/
+
+class A {
+  List<int> dailyTemperatures(List<int> temperatures) {
+    List<int> res = List.filled(temperatures.length, 0);
+    for (int i = temperatures.length - 2; i >= 0; i--) {
+      int next = i + 1;
+      while (
+          next < temperatures.length && temperatures[next] <= temperatures[i]) {
+        if (res[next] == 0) {
+          next = temperatures.length;
+          break;
+        }
+        next += res[next];
+      }
+      if (next < temperatures.length) {
+        res[i] = next - i;
+      }
+    }
+    return res;
+  }
+}
+
+class B {
+  // TLE
+  List<int> dailyTemperatures(List<int> temperatures) {
+    List<int> ar = List.filled(temperatures.length, 0);
+    if (temperatures.length == 1) {
+      ar[0] = 0;
+    } else {
+      for (int x = 0; x < temperatures.length; x++) {
+        int p = 0;
+        // int q = 0;
+        for (int y = x + 1; y < temperatures.length; y++) {
+          if (temperatures[x] < temperatures[y]) {
+            ar[x] = (y - x).abs();
+            p++;
+            break;
+          }
+        }
+        if (p == 0) {
+          ar[x] = 0;
+        }
+      }
+    }
+    return ar;
+  }
+}
+
+class C {
+  List<int> dailyTemperatures(List<int> temperatures) {
+    if (temperatures.isEmpty || temperatures.length == 0) {
+      return [0];
+    }
+    int n = temperatures.length;
+    List<int> res = List.filled(temperatures.length, 0);
+    List<int> stack = [];
+    for (int j = n - 1; j >= 0; j--) {
+      while (stack.isNotEmpty && temperatures[stack.last] <= temperatures[j])
+        stack.removeLast();
+      res[j] = stack.isEmpty ? 0 : stack.last - j;
+      stack.add(j);
+    }
+    return res;
+  }
+}

DailyTemperatures/daily_temperatures.go

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+package main
+
+func dailyTemperatures(temperatures []int) []int {
+	var res []int = make([]int, len(temperatures))
+	for i := len(temperatures) - 2; i >= 0; i-- {
+		var next int = i + 1
+		for next < len(temperatures) && temperatures[next] <= temperatures[i] {
+			if res[next] == 0 {
+				next = len(temperatures)
+				break
+			}
+			next += res[next]
+		}
+		if next < len(temperatures) {
+			res[i] = next - i
+		}
+	}
+	return res
+}

DailyTemperatures/daily_temperatures.md

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+# 🔥 Daily Temperatures 🔥 || 3 Approaches || Simple Fast and Easy || with Explanation
+
+## Explanation
+
+### Idea
+
+First, make a monotonic stack  for calculating the next greater element:
+
+Then we will traverse the temperatures array and perform the following operations for every index i:
+
+If the stack is not empty, then we will store the index presently at the top of the stack in a variable index. If the temperature on the ith  day is strictly greater than that at the index'th day, then we will update the ans[i] with index-i days as we have found a  temperature higher than the current day. The index is removed from the stack i.e perform a pop operation on the stack.
+The above step continues till the temperature at the ith  day is strictly lesser than that at the index'th day.
+If the above steps continue, we will update the ans array at positions less than i.
+In the end, we will push the current iteration i into the stack.
+Finally, we get the answer array with the number of days we have to wait to get a higher temperature for the current days.
+
+#### - Time Complexity
+
+The time complexity of the above code is O(n).
+
+#### - Space Complexity
+
+The space complexity of the above code is O(n).
+
+## Solution - 1
+
+```dart
+class Solution {
+  List<int> dailyTemperatures(List<int> temperatures) {
+    List<int> res = List.filled(temperatures.length, 0);
+    for (int i = temperatures.length - 2; i >= 0; i--) {
+      int next = i + 1;
+      while (
+          next < temperatures.length && temperatures[next] <= temperatures[i]) {
+        if (res[next] == 0) {
+          next = temperatures.length;
+          break;
+        }
+        next += res[next];
+      }
+      if (next < temperatures.length) {
+        res[i] = next - i;
+      }
+    }
+    return res;
+  }
+}
+```
+
+## Solution - 2
+
+```dart
+class Solution {
+  // TLE
+  List<int> dailyTemperatures(List<int> temperatures) {
+    List<int> ar = List.filled(temperatures.length, 0);
+    if (temperatures.length == 1) {
+      ar[0] = 0;
+    } else {
+      for (int x = 0; x < temperatures.length; x++) {
+        int p = 0;
+        for (int y = x + 1; y < temperatures.length; y++) {
+          if (temperatures[x] < temperatures[y]) {
+            ar[x] = (y - x).abs();
+            p++;
+            break;
+          }
+        }
+        if (p == 0) {
+          ar[x] = 0;
+        }
+      }
+    }
+    return ar;
+  }
+}
+```
+
+## Solution - 3
+
+```dart
+class Solution {
+  List<int> dailyTemperatures(List<int> temperatures) {
+    if (temperatures.isEmpty || temperatures.length == 0) {
+      return [0];
+    }
+    int n = temperatures.length;
+    List<int> res = List.filled(temperatures.length, 0);
+    List<int> stack = [];
+    for (int j = n - 1; j >= 0; j--) {
+      while (stack.isNotEmpty && temperatures[stack.last] <= temperatures[j])
+        stack.removeLast();
+      res[j] = stack.isEmpty ? 0 : stack.last - j;
+      stack.add(j);
+    }
+    return res;
+  }
+}
+```

README.md

@@ -169,6 +169,7 @@ This repo contain leetcode solution using DART and GO programming language. Most
 - [**198.** House Robber](HouseRobber/house_robber.dart)
 - [**1143.** Longest Common Subsequence](LongestCommonSubsequence/longest_common_subsequence.dart)
 - [**150.** Evaluate Reverse Polish Notation](EvaluateReversePolishNotation/evaluate_reverse_polish_notation.dart)
+- [**739.** Daily Temperatures](DailyTemperatures/daily_temperatures.dart)
 
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