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Copy pathSearch2DMatrix.java
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239 lines (196 loc) · 4.66 KB
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public class Search2DMatrix {
public static void main(String[] args) {
int[][] matrix = { { 1, 3, 5, 7 }, { 10, 11, 16, 20 },
{ 23, 30, 34, 50 } };
// int[][] matrix = {{1,1},{3,3}};
// int[][] matrix =
// {{-9,-9,-9,-7,-5,-3,-3,-3},{-2,-2,0,1,2,3,3,4},{5,5,5,7,9,11,11,12},{14,14,15,16,18,18,19,20},{21,23,24,25,27,29,30,31},{34,35,37,38,38,38,40,40},{42,44,44,45,47,47,47,48},{50,51,51,52,53,54,56,56},{58,59,60,62,64,64,64,66}};
// {{1,3,5,7},{10,11,16,20},{23,30,34,50}};
Search2DMatrix m = new Search2DMatrix();
int target = 21;
System.out.println(m.searchMatrix_b(matrix, target));
}
public boolean searchMatrix_b(int[][] matrix, int target) {
// null
if (matrix == null)
return false;
// out of bounds
if(target < matrix[0][0] || target > matrix[matrix.length - 1][matrix[0].length - 1])
return false;
// single
if (matrix.length == 1 && matrix[0].length == 1)
return (matrix[0][0] == target);
// row
if (matrix.length == 1)
return searchRow(matrix, target);
// column
if (matrix[0].length == 1)
return searchCol(matrix, target);
int imin = 0;
int imax = matrix.length - 1;
int prev = -1;
int row = -1;
int imid = 0;
// vertical
while (imax >= imin) {
// System.out.println(imin + " " + imax);
imid = (imin + imax) / 2;
System.out.println("MID " + matrix[imid][0]);
if(matrix[imid][0] == target) // if we found it we're done
return true;
else if (prev == 0 && matrix[imid-1][0] < target && matrix[imid][0] > target) // need to check if target is between the column values
{
row = imid - 1;
break;
}
else if(prev == 1 && matrix[imid + 1][0] > target && matrix[imid][0] < target) // checks if >
{
row = imid - 1;
break;
}
else if (matrix[imid][0] < target) // binary search
{
imin = imid + 1;
prev = 0;
}
else if(matrix[imid][0] > target)
{
imax = imid - 1;
prev = 1;
}
// System.out.println(imid + " " + imax);
}
System.out.println("IGNORE " + row);
// pretty sure this isn't used anymore
if(row == -1)
{
if(matrix[0][0] > target)
return false;
else if(matrix[imid][0] < target)
row = imid;
}
// System.out.println("ROW " + row);
imin = 0;
imax = matrix[0].length;
// binary horizontal
while(imax >= imin)
{
imid = (imax + imin) / 2;
// System.out.println(imid);
if(imid >= matrix[0].length)
return false;
if(matrix[row][imid] == target)
return true;
else if(matrix[row][imid] < target)
{
imin = imid + 1;
prev = matrix[row][imid];
}
else
{
imax = imid - 1;
prev = matrix[row][imid];
}
}
return false;
}
/**
* search a single colum matrix
*
* @param matrix
* @param target
* @return
*/
private boolean searchCol(int[][] matrix, int target) {
int imin = 0;
int imax = matrix.length - 1;
while(imax >= imin)
{
int imid = (imax + imin) / 2;
if(matrix[imid][0] == target)
return true;
else if(matrix[imid][0] < target)
imin = imid + 1;
else
imax = imid - 1;
}
return false;
}
/**
* search a single row matrix
*
* @param matrix
* @param target
* @return
*/
private boolean searchRow(int[][] matrix, int target) {
int imin = 0;
int imax = matrix[0].length - 1;
while(imax >= imin)
{
int imid = (imax + imin) / 2;
// System.out.println(matrix[0][imid]);
if(matrix[0][imid] == target)
return true;
else if(matrix[0][imid] < target)
imin = imid + 1;
else
imax = imid - 1;
}
return false;
}
/**
* iterative approach
*
* @param matrix
* @param target
* @return
*/
public boolean searchMatrix(int[][] matrix, int target) {
int i = 0;
int j = 0;
// null
if (matrix == null)
return false;
// single
if (matrix.length == 1 && matrix[0].length == 1)
return (matrix[0][0] == target);
// row
if (matrix.length == 1) {
for (; i < matrix[0].length; i++) {
if (matrix[j][i] == target)
return true;
}
return false;
}
// col
if (matrix[0].length == 1) {
// System.out.println("col");
for (; i < matrix.length; i++) {
// System.out.println(matrix[i][j]);
if (matrix[i][j] == target)
return true;
}
return false;
}
while (true) {
// System.out.println("LOOKING AT " + matrix[i + 1][j]);
if (matrix[i + 1][j] == target)
return true;
if (matrix[i + 1][j] > target) {
// binary search
for (; j < matrix[0].length; j++) {
// System.out.println("LOOKING AT " + matrix[i][j]);
if (matrix[i][j] == target)
return true;
}
return false;
} else {
i++;
}
if (i == matrix.length)
break;
}
return false;
}
}