classSolution {

funnumSubmatrixSumTarget(matrix:Array<IntArray>,target:Int):Int {

val n= matrix.size

val m= matrix[0].size

val prefix=Array (n) {IntArray (m) }

for (iin0 until n) {

for (jin0 until m) {

val top=if (i>0) prefix[i-1][j]else0

val left=if (j>0) prefix[i][j-1]else0

val topLeft=if (minOf(i, j)>0) prefix[i-1][j-1]else0

prefix[i][j]= matrix[i][j]+ top+ left- topLeft

}

}

var res=0

for (iin0 until n) {

for (i2in i until n) {

var count=HashMap<Int,Int>()

count[0]=1

for (jin0 until m) {

val curSum= prefix[i2][j]- (if (i>0) prefix[i-1][j]else0)

val diff= curSum- target

res+= (count[diff]?:0)

count[curSum]= (count[curSum]?:0)+1

}

}

}

return res

}

}