🚀 13-Sep-2020

Author: sureshmangs

competitive programming/leetcode/1582. Special Positions in a Binary Matrix.cpp

@@ -0,0 +1,95 @@
+Given a rows x cols matrix mat, where mat[i][j] is either 0 or 1, return the number of special positions in mat.
+
+A position (i,j) is called special if mat[i][j] == 1 and all other elements in row i and column j are 0 (rows and columns are 0-indexed).
+
+
+
+Example 1:
+
+Input: mat = [[1,0,0],
+              [0,0,1],
+              [1,0,0]]
+Output: 1
+Explanation: (1,2) is a special position because mat[1][2] == 1 and all other elements in row 1 and column 2 are 0.
+Example 2:
+
+Input: mat = [[1,0,0],
+              [0,1,0],
+              [0,0,1]]
+Output: 3
+Explanation: (0,0), (1,1) and (2,2) are special positions.
+Example 3:
+
+Input: mat = [[0,0,0,1],
+              [1,0,0,0],
+              [0,1,1,0],
+              [0,0,0,0]]
+Output: 2
+Example 4:
+
+Input: mat = [[0,0,0,0,0],
+              [1,0,0,0,0],
+              [0,1,0,0,0],
+              [0,0,1,0,0],
+              [0,0,0,1,1]]
+Output: 3
+
+
+Constraints:
+
+rows == mat.length
+cols == mat[i].length
+1 <= rows, cols <= 100
+mat[i][j] is 0 or 1.
+
+
+
+
+
+
+
+
+class Solution {
+public:
+
+    bool isSpecial(vector<vector<int> > &mat, int i, int j){
+        int m=mat.size();
+        int n=mat[0].size();
+
+        for(int x=0;x<n;x++)
+            if(mat[i][x]==1 && x!=j) return false;
+
+        for(int x=0;x<m;x++)
+            if(mat[x][j]==1 && x!=i) return false;
+
+        return true;
+    }
+
+    int numSpecial(vector<vector<int>>& mat) {
+
+        int m=mat.size();
+        if(m==0) return 0;
+        int n=mat[0].size();
+
+        int cnt=0;
+
+        for(int i=0;i<m;i++){
+            for(int j=0;j<n;j++){
+                if(mat[i][j] && isSpecial(mat, i, j))
+                    cnt++;
+            }
+        }
+        return cnt;
+    }
+};
+
+
+
+
+
+/* Alter
+1. Get the sum of all the rows
+2. Get the sum of all the coloumns
+3. Traverse the matrix and whenever encounter 1 check its row and col sum, if 1 then increment count by 1.
+4. Return count
+*/