java-35.求一个矩阵中最大的二维矩阵 ( 元素和最大 )

the idea is from: http://blog.csdn.net/zhanxinhang/article/details/6731134
```
public class MaxSubMatrix {

/**see http://blog.csdn.net/zhanxinhang/article/details/6731134
* Q35

1 2 0 3 4
2 3 4 5 1
1 1 5 3 0

4 5
5 3
three solutions:
1.brutalFind:calculate all the possible sum and find the largest
2.verticalFind:when matrix's rowIndex is larger than columnIndex,like "int[][] b" in the following code
3.herizonalFind:when matrix's rowIndex is smaller than columnIndex,like "int[][] a" in the following code
both 2 and 3 avoid duplicate calculation
*/
public static void main(String[] args) {
MaxSubMatrix msm=new MaxSubMatrix();
int[][] a={
{2,3,4},
{1,3,3},
{1,4,6},
{1,4,8},
{2,3,2},
};
int[][] b={
{1, 2, 0, 3, 4},
{2, 3, 4, 5, 1},
{1, 1, 5, 3, 0},
};

int[][] result=msm.findSumMaxSubMatrix(a);
msm.printArray(result);
System.out.println("----------------");
result=msm.brutalFind(a);
msm.printArray(result);
System.out.println("----------------");

result=msm.findSumMaxSubMatrix(b);
msm.printArray(result);
System.out.println("----------------");
result=msm.brutalFind(b);
msm.printArray(result);
}

public int[][] findSumMaxSubMatrix(int[][] a){
int[][] result=null;
int row=a.length;
int col=a[0].length;
if(row>=col){
result=herizonalFind(a,row,col);
}else{
result=verticalFind(a,row,col);
}
return result;
}

public int[][] brutalFind(int[][] a){
int[][] result=new int[2][2];
int row=a.length;
int col=a[0].length;
int sum=0;
int p=0;
int q=0;
for(int i=0;i<row-1;i++){
for(int j=0;j<col-1;j++){
int x=a[i][j];
int y=a[i][j+1];
int z=a[i+1][j];
int k=a[i+1][j+1];
int temp=x+y+z+k;
if(temp>sum){
sum=temp;
p=i;
q=j;
}
}
}
result[0][0]=a[p][q];
result[0][1]=a[p][q+1];
result[1][0]=a[p+1][q];
result[1][1]=a[p+1][q+1];
return result;
}

public int[][] herizonalFind(int[][] a,int row,int col){
int[][] result=new int[2][2];
int lastHerizonalSum=a[0][0]+a[0][1];
int sum=0;
int p=0;
int q=0;
for(int i=1;i<row;i++){
for(int j=0;j<col-1;j++){
int temp=lastHerizonalSum+a[i][j]+a[i][j+1];
lastHerizonalSum=a[i][j]+a[i][j+1];
if(temp>sum){
sum=temp;
p=i;
q=j;
}
}
}
result[0][0]=a[p-1][q];
result[0][1]=a[p-1][q+1];
result[1][0]=a[p][q];
result[1][1]=a[p][q+1];
return result;
}

public int[][] verticalFind(int[][] a,int row,int col){
int[][] result=new int[2][2];
int lastVerticalSum=a[0][0]+a[1][0];
int sum=0;
int p=0;
int q=0;
for(int i=0;i<row-1;i++){
for(int j=1;j<col;j++){
int temp=lastVerticalSum+a[i][j]+a[i+1][j];
lastVerticalSum=a[i][j]+a[i+1][j];
if(temp>sum){
sum=temp;
p=i;
q=j;
}
}
}
result[0][0]=a[p][q-1];
result[0][1]=a[p][q];
result[1][0]=a[p+1][q-1];
result[1][1]=a[p+1][q];
return result;
}

public void printArray(int[][] a){
int row=a.length;
int col=a[0].length;
for(int i=0;i<row;i++){
for(int j=0;j<col;j++){
System.out.print(a[i][j]+" ");
}
System.out.println();
}
}
}

```

java-35.求一个矩阵中最大的二维矩阵 ( 元素和最大 )

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