Cells with Odd Values in a Matrix
给一个2d数组, 里面是横竖的index, 求在index上+1后matrix的奇数个数. 这个题我看有O(n)解法, 我自己做的是n^2
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class Solution { public int oddCells(int n, int m, int[][] indices) { int[] row = new int[n]; int[] col = new int[m]; for(int[] i : indices) { row[i[0]]++; col[i[1]]++; } int count = 0; for(int i = 0; i < n; i++) { for(int j = 0; j < m; j++){ if((row[i]+col[j]) % 2 != 0) count++; } } return count; } } |
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class Solution { public int oddCells(int n, int m, int[][] indices) { int[] row = new int[n]; int[] col = new int[m]; for(int[] i : indices) { row[i[0]]++; col[i[1]]++; } int count = 0; for(int i = 0; i < n; i++) { if(row[i] % 2 != 0) // if odd count++; } int res = 0; for(int i = 0; i < m; i++) { if(col[i] % 2 != 0) // if odd res += (n - count); // odd + odd = even else res += count;// odd + even = odd } return res; } } |