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Commitde52e0c

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add a solution for 542
1 parent829f5a5 commitde52e0c

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2 files changed

+106
-17
lines changed

2 files changed

+106
-17
lines changed

‎src/main/java/com/fishercoder/solutions/_542.java

Lines changed: 70 additions & 17 deletions
Original file line numberDiff line numberDiff line change
@@ -3,40 +3,93 @@
33
importjava.util.Deque;
44
importjava.util.LinkedList;
55
importjava.util.List;
6+
importjava.util.Queue;
67

78
publicclass_542 {
89

910
publicstaticclassSolution1 {
10-
11-
publicList<List<Integer>>updateMatrix(List<List<Integer>>matrix) {
12-
intm =matrix.size();
13-
intn =matrix.get(0).size();
11+
publicint[][]updateMatrix(int[][]mat) {
12+
intm =mat.length;
13+
intn =mat[0].length;
14+
int[][]ans =newint[m][n];
1415
Deque<int[]>deque =newLinkedList<>();
1516
for (inti =0;i <m;i++) {
1617
for (intj =0;j <n;j++) {
17-
if (matrix.get(i).get(j) ==0) {
18+
if (mat[i][j] ==0) {
1819
deque.offer(newint[]{i,j});
1920
}else {
20-
matrix.get(i).set(j,Integer.MAX_VALUE);
21+
ans[i][j] =m *n;
2122
}
2223
}
2324
}
24-
25-
finalint[]dirs =newint[]{0,1,0, -1,0};
25+
int[]directions =newint[]{0,1,0, -1,0};
2626
while (!deque.isEmpty()) {
27-
int[]currentCell =deque.poll();
28-
for (inti =0;i <dirs.length -1;i++) {
29-
intnextRow =currentCell[0] +dirs[i];
30-
intnextCol =currentCell[1] +dirs[i +1];
31-
if (nextRow <0 ||nextCol <0 ||nextRow >=m ||nextCol >=n ||matrix.get(nextRow).get(nextCol) <=matrix.get(currentCell[0]).get(currentCell[1]) +1) {
32-
continue;
27+
int[]curr =deque.poll();
28+
for (inti =0;i <directions.length -1;i++) {
29+
intnextX =directions[i] +curr[0];
30+
intnextY =directions[i +1] +curr[1];
31+
if (nextX >=0 &&nextX <m &&nextY >=0 &&nextY <n &&ans[nextX][nextY] >ans[curr[0]][curr[1]] +1) {
32+
deque.offer(newint[]{nextX,nextY});
33+
ans[nextX][nextY] =ans[curr[0]][curr[1]] +1;
3334
}
34-
deque.offer(newint[]{nextRow,nextCol});
35-
matrix.get(nextRow).set(nextCol,matrix.get(currentCell[0]).get(currentCell[1]) +1);
3635
}
3736
}
38-
returnmatrix;
37+
returnans;
3938
}
4039
}
4140

41+
publicstaticclassSolution2 {
42+
/**
43+
* A silly, but working solution. Apparently, the above BFS approach is a smarter version of this one.
44+
*/
45+
publicint[][]updateMatrix(int[][]mat) {
46+
intm =mat.length;
47+
intn =mat[0].length;
48+
int[][]ans =newint[m][n];
49+
Queue<int[]>queue =newLinkedList<>();
50+
for (inti =0;i <m;i++) {
51+
for (intj =0;j <n;j++) {
52+
if (mat[i][j] ==0) {
53+
queue.offer(newint[]{i,j});
54+
}else {
55+
ans[i][j] =m *n;
56+
}
57+
}
58+
}
59+
while (!queue.isEmpty()) {
60+
int[]curr =queue.poll();
61+
for (inti =curr[0] +1,j =curr[1];i <m &&mat[i][j] !=0;i++) {
62+
ans[i][j] =Math.min(ans[i][j],i -curr[0]);
63+
}
64+
for (inti =curr[0] -1,j =curr[1];i >=0 &&mat[i][j] !=0;i--) {
65+
ans[i][j] =Math.min(ans[i][j],curr[0] -i);
66+
}
67+
for (intj =curr[1] +1,i =curr[0];j <n &&mat[i][j] !=0;j++) {
68+
ans[i][j] =Math.min(ans[i][j],j -curr[1]);
69+
}
70+
for (intj =curr[1] -1,i =curr[0];j >=0 &&mat[i][j] !=0;j--) {
71+
ans[i][j] =Math.min(ans[i][j],curr[1] -j);
72+
}
73+
}
74+
for (inti =0;i <m;i++) {
75+
for (intj =0;j <n;j++) {
76+
if (i +1 <m &&ans[i +1][j] >=1) {
77+
ans[i][j] =Math.min(ans[i][j],ans[i +1][j] +1);
78+
}
79+
if (i -1 >=0 &&ans[i -1][j] >=1) {
80+
ans[i][j] =Math.min(ans[i][j],ans[i -1][j] +1);
81+
}
82+
if (j +1 <n &&ans[i][j +1] >=1) {
83+
ans[i][j] =Math.min(ans[i][j],ans[i][j +1] +1);
84+
}
85+
if (j -1 >=0 &&ans[i][j -1] >=1) {
86+
ans[i][j] =Math.min(ans[i][j],ans[i][j -1] +1);
87+
}
88+
}
89+
}
90+
returnans;
91+
}
92+
93+
}
94+
4295
}
Lines changed: 36 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,36 @@
1+
packagecom.fishercoder;
2+
3+
importcom.fishercoder.common.utils.CommonUtils;
4+
importcom.fishercoder.solutions._542;
5+
importorg.junit.BeforeClass;
6+
importorg.junit.Test;
7+
8+
importstaticorg.junit.Assert.assertEquals;
9+
10+
publicclass_542Test {
11+
privatestatic_542.Solution1solution1;
12+
privatestatic_542.Solution2solution2;
13+
14+
@BeforeClass
15+
publicstaticvoidsetup() {
16+
solution1 =new_542.Solution1();
17+
solution2 =new_542.Solution2();
18+
}
19+
20+
@Test
21+
publicvoidtest1() {
22+
int[][]matrix =CommonUtils.convertLeetCodeIrregularLengths2DArrayInputIntoJavaArray("[1,1,0,1,1,1,1,1,1,1],[1,1,0,1,1,1,1,1,1,1],[1,1,1,1,0,0,0,1,1,0],[1,1,1,1,1,1,0,0,1,0],[1,0,0,1,1,1,0,1,0,1],[0,0,1,0,0,1,1,0,0,1],[0,1,0,1,1,1,1,1,1,1],[1,0,0,1,1,0,0,0,0,0],[0,0,1,1,1,1,0,1,1,1],[1,1,0,0,1,0,1,0,1,1]");
23+
int[][]expected =CommonUtils.convertLeetCodeIrregularLengths2DArrayInputIntoJavaArray("[2,1,0,1,2,2,2,3,3,2],[2,1,0,1,1,1,1,2,2,1],[3,2,1,1,0,0,0,1,1,0],[2,1,1,2,1,1,0,0,1,0],[1,0,0,1,1,1,0,1,0,1],[0,0,1,0,0,1,1,0,0,1],[0,1,0,1,1,1,1,1,1,1],[1,0,0,1,1,0,0,0,0,0],[0,0,1,1,2,1,0,1,1,1],[1,1,0,0,1,0,1,0,1,2]");
24+
assertEquals(expected,solution1.updateMatrix(matrix));
25+
assertEquals(expected,solution2.updateMatrix(matrix));
26+
}
27+
28+
@Test
29+
publicvoidtest2() {
30+
int[][]matrix =CommonUtils.convertLeetCodeIrregularLengths2DArrayInputIntoJavaArray("[0,0,0],[0,1,0],[0,0,0]");
31+
int[][]expected =CommonUtils.convertLeetCodeIrregularLengths2DArrayInputIntoJavaArray("[0,0,0],[0,1,0],[0,0,0]");
32+
assertEquals(expected,solution1.updateMatrix(matrix));
33+
assertEquals(expected,solution2.updateMatrix(matrix));
34+
}
35+
36+
}

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