Create max_increase_to_keep_city_skyline.cpp

Author: avidLearnerInProgress

max_increase_to_keep_city_skyline.cpp

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+class Solution {
+public:
+    //TC: O(n*2) SC: O(n) => don't think its possible in anything less than n * 2
+    int maxIncreaseKeepingSkyline(vector<vector<int>>& grid) {
+        
+        int n = grid.size();
+        vector<int> maxIncreaseInRow(n, 0);
+        vector<int> maxIncreaseInCol(n, 0); // n * n
+        int maxSumIncrease = 0;
+        
+        
+        //for any skyline problem we consider the max at any index...
+        //so for any index(i, j) in grid => we can grow the current building to the height of min from maxInCol or maxInRow.
+        
+        //get max for every row and every column
+        for(int i = 0; i < n; ++i) {
+            for(int j = 0; j < n; ++j) {
+                maxIncreaseInRow[i] = max(maxIncreaseInRow[i], grid[i][j]);
+                maxIncreaseInCol[j] = max(maxIncreaseInCol[j], grid[i][j]);
+            }
+        }
+        
+        //simple math - 
+            // take min of both maxRow and maxCol at i and j indexes.
+            // min because we don't want to change the skyline. 
+            // example: maxIncreaseInRow[i] > grid[i][j] => this operation will change the skyline.
+        for(int i = 0; i < n; ++i) {
+            for(int j = 0; j < n; ++j) {
+                maxSumIncrease += min(maxIncreaseInRow[i], maxIncreaseInCol[j]) - grid[i][j];
+            }
+        }
+        
+        return maxSumIncrease;
+        
+    }
+};