maximal-rectangle

自己做个笔记用

public class Solution {

public int maximalRectangle ( char [][] matrix ){

if ( matrix == null || matrix . length == 0 || matrix [ 0 ]. length == 0 )

return 0 ;

int [] height = new int [ matrix [ 0 ]. length ];

for ( int i == 0 ; i < matrix [ 0 ]. length ; i ++){

if ( matrix [ 0 ][ i ]== "1" )

height [ i ]== 1 ;

}

int result = largestInLine ( height );

for ( int i = 1 ; i < matrix . length ; i ++){

resetHeight ( matrix , height , i );

result = Math . max ( result , largestInLine ( height ));

}

return result ;

}

//为每行维护的数组，用于储存高度

public int largestInLine ( int [] height ){

if ( height == null || height . length == 0 )

return 0 ;

int len = height . length ;

Stack < Integer > s = new Stack < Integer >();

int maxArea = 0 ;

for ( int i = 0 ; i <= len ; i ++){

int h =( i == len ? 0 : height [ i ]);

if ( s . isEmpty () || h >= height [ s . peek ()]){

s . push ( i );

} else {

int tp = s . pop ();

maxArea = Math . max ( maxArea , height [ tp ]*( s . isEmpty ()? i: i - 1 - s . peek ()));

i -- ；

}

}

return maxArea ;

}

//重置高度，用以扫描整个矩阵

private void resetHeight ( char [][] matrix , int [] height , int idx ){

for ( int i = 0 ; i < matrix [ 0 ]. length ; i ++){

if ( matrix [ idx ][ i ]== '1' )

height [ i ]+= 1 ;

else

height [ i ]= 0 ;

}

}

}