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62 lines (56 loc) · 2.44 KB
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// Given a 2D binary matrix filled with 0's and 1's,
// find the largest square containing only 1's and return its area.
// See: https://leetcode.com/problems/maximal-square/
package leetcode.dynamic_programming;
public class MaximalSquare {
public int maximalSquare(char[][] matrix) {
if (matrix.length == 0) {
return 0;
}
int max = 0;
int[][] dp = new int[matrix.length][matrix[0].length];
for (int i = 0; i < dp.length; i++) {
for (int j = 0; j < dp[0].length; j++) {
dp[i][j] = matrix[i][j] == '1' ? 1 : 0;
}
}
for (int i = 0; i < dp.length; i++) {
for (int j = 0; j < dp[0].length; j++) {
if (matrix[i][j] == '1' && i > 0 & j > 0) {
dp[i][j] = Math.min(dp[i - 1][j - 1], Math.min(dp[i][j - 1], dp[i - 1][j])) + 1;
max = Math.max(dp[i][j], max);
} else if (matrix[i][j] == '1'){
max = Math.max(1, max);
}
}
}
return max * max;
}
public static void main(String[] args) {
MaximalSquare sln = new MaximalSquare();
System.out.println(sln.maximalSquare(new char[][] {
{ '1', '0', '1', '0', '0' },
{ '1', '0', '1', '1', '1' },
{ '1', '1', '1', '1', '1' },
{ '1', '0', '0', '1', '0' } })); // 4
System.out.println(sln.maximalSquare(new char[][] {})); // 0
System.out.println(sln.maximalSquare(new char[][] {{'1'}})); // 1
System.out.println(sln.maximalSquare(new char[][] {{'1', '1'}, {'1', '1'}})); // 4
System.out.println(sln.maximalSquare(new char[][] {
{ '1', '0', '1', '0'},
{ '1', '0', '1', '1'},
{ '1', '0', '1', '1'},
{ '1', '1', '1', '1'} })); // 4
System.out.println(sln.maximalSquare(new char[][] {
{'1','0','1','0','0','1','1','1','0'},
{'1','1','1','0','0','0','0','0','1'},
{'0','0','1','1','0','0','0','1','1'},
{'0','1','1','0','0','1','0','0','1'},
{'1','1','0','1','1','0','0','1','0'},
{'0','1','1','1','1','1','1','0','1'},
{'1','0','1','1','1','0','0','1','0'},
{'1','1','1','0','1','0','0','0','1'},
{'0','1','1','1','1','0','0','1','0'},
{'1','0','0','1','1','1','0','0','0'}})); // 4
}
}