562. Longest Line of Consecutive One in Matrix
package LeetCode_562 /** * 562. Longest Line of Consecutive One in Matrix * (Prime) *Given a 01 matrix M, find the longest line of consecutive one in the matrix. * The line could be horizontal, vertical, diagonal or anti-diagonal. Example: Input: [[0,1,1,0], [0,1,1,0], [0,0,0,1]] Output: 3 Hint: The number of elements in the given matrix will not exceed 10,000. * */ class Solution { /* * solution: scan horizontal,vertical,diagonal, anti-diagonal for each node and calculate current consecutive one, * Time:O(m^2 * n^2), Space:O(1) * */ fun longestLine(grid: Array<IntArray>): Int { if (grid == null || grid.isEmpty()) { return 0 } val m = grid.size val n = grid[0].size var max = 0 val directions = arrayOf( intArrayOf(1,0),//horizontal intArrayOf(0,1),//vertical intArrayOf(-1,1),//diagonal intArrayOf(-1,-1)//anti-diagonal ) for (i in 0 until m) { for (j in 0 until n) { //expand current position where was 1 if (grid[i][j] == 0) { continue } for (d in 0 until 4) { var cur = 0 var x = i var y = j while (x >= 0 && x < m && y >= 0 && y < n && grid[x][y] == 1) { x += directions[d][0] y += directions[d][1] cur++ } max = Math.max(cur, max) } } } return max } }