day 15

Author: sachuverma

Leetcode Daily Challenge/February-2021/15. The K Weakest Rows in a Matrix.cpp

@@ -0,0 +1,75 @@
+/*
+The K Weakest Rows in a Matrix
+==============================
+
+Given a m * n matrix mat of ones (representing soldiers) and zeros (representing civilians), return the indexes of the k weakest rows in the matrix ordered from the weakest to the strongest.
+
+A row i is weaker than row j, if the number of soldiers in row i is less than the number of soldiers in row j, or they have the same number of soldiers but i is less than j. Soldiers are always stand in the frontier of a row, that is, always ones may appear first and then zeros.
+
+Example 1:
+Input: mat = 
+[[1,1,0,0,0],
+ [1,1,1,1,0],
+ [1,0,0,0,0],
+ [1,1,0,0,0],
+ [1,1,1,1,1]], 
+k = 3
+Output: [2,0,3]
+Explanation: 
+The number of soldiers for each row is: 
+row 0 -> 2 
+row 1 -> 4 
+row 2 -> 1 
+row 3 -> 2 
+row 4 -> 5 
+Rows ordered from the weakest to the strongest are [2,0,3,1,4]
+
+Example 2:
+Input: mat = 
+[[1,0,0,0],
+ [1,1,1,1],
+ [1,0,0,0],
+ [1,0,0,0]], 
+k = 2
+Output: [0,2]
+Explanation: 
+The number of soldiers for each row is: 
+row 0 -> 1 
+row 1 -> 4 
+row 2 -> 1 
+row 3 -> 1 
+Rows ordered from the weakest to the strongest are [0,2,3,1]
+
+Constraints:
+m == mat.length
+n == mat[i].length
+2 <= n, m <= 100
+1 <= k <= m
+matrix[i][j] is either 0 or 1.
+
+Hint #1  
+Sort the matrix row indexes by the number of soldiers and then row indexes.
+*/
+
+class Solution
+{
+public:
+  vector<int> kWeakestRows(vector<vector<int>> &mat, int k)
+  {
+    vector<vector<int>> count;
+    for (int i = 0; i < mat.size(); ++i)
+    {
+      int sum = 0;
+      for (int j = 0; j < mat[0].size(); ++j)
+      {
+        sum += mat[i][j];
+      }
+      count.push_back({sum, i});
+    }
+    sort(count.begin(), count.end());
+    vector<int> ans;
+    for (int i = 0; i < k; ++i)
+      ans.push_back(count[i][1]);
+    return ans;
+  }
+};

Leetcode Daily Challenge/February-2021/README.MD

@@ -11,10 +11,11 @@
 | 7.  | [Shortest Distance to a Character](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/584/week-1-february-1st-february-7th/3631/) | [cpp](./07.%20Shortest%20Distance%20to%20a%20Character.cpp) | 
 | 8.  | [Peeking Iterator](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3633/) | [cpp](./08.%20Peeking%20Iterator.cpp) | 
 | 9.  | [Convert BST to Greater Tree](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3634/) | [cpp](./09.%20Convert%20BST%20to%20Greater%20Tree.cpp) | 
-| 10.  | [Copy List with Random Pointer](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3635/) | [cpp](./10.%20Copy%20List%20with%20Random%20Pointer.cpp) | 
-| 11.  | [Valid Anagram](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3636/) | [cpp](./11.%20Valid%20Anagram.cpp) | 
-| 12.  | [Number of Steps to Reduce a Number to Zero](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3637/) | [cpp](./12.%20Number%20of%20Steps%20to%20Reduce%20a%20Number%20to%20Zero.cpp) | 
-| 13.  | [Shortest Path in Binary Matrix](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3638/) | [cpp](./13.%20Shortest%20Path%20in%20Binary%20Matrix.cpp) | 
-| 14.  | [Is Graph Bipartite?](https://leetcode.com/explore/featured/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3639/) | [cpp](./14.%20Is%20Graph%20Bipartite.cpp) | 
+| 10.  | [Copy List with Random Pointer](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3635/) | [cpp](./10.%20Copy%20List%20with%20Random%20Pointer.cpp) |  
+| 11.  | [Valid Anagram](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3636/) | [cpp](./11.%20Valid%20Anagram.cpp) |  
+| 12.  | [Number of Steps to Reduce a Number to Zero](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3637/) | [cpp](./12.%20Number%20of%20Steps%20to%20Reduce%20a%20Number%20to%20Zero.cpp) |  
+| 13.  | [Shortest Path in Binary Matrix](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3638/) | [cpp](./13.%20Shortest%20Path%20in%20Binary%20Matrix.cpp) |  
+| 14.  | [Is Graph Bipartite?](https://leetcode.com/explore/featured/card/february-leetcoding-challenge-2021/585/week-2-february-8th-february-14th/3639/) | [cpp](./14.%20Is%20Graph%20Bipartite.cpp) |  
+| 15.  | [The K Weakest Rows in a Matrix](https://leetcode.com/explore/challenge/card/february-leetcoding-challenge-2021/586/week-3-february-15th-february-21st/3641/) | [cpp](./15.%20The%20K%20Weakest%20Rows%20in%20a%20Matrix.cpp) |