Create week 5 542. 01 Matrix

Author: andysli6590

week 5 542. 01 Matrix

@@ -0,0 +1,69 @@
+public class Solution {
+    int row;
+    int col;
+    
+    int [] dx = {1, -1, 0, 0};
+    int [] dy = {0, 0, 1, -1};
+    
+    public List<List<Integer>> updateMatrix(List<List<Integer>> matrix){
+        
+        if (matrix == null || matrix.size() == 0 || matrix.get(0).size() == 0){
+            return matrix;
+        }
+        row = matrix.size();
+        col = matrix.get(0).size();
+        preSet(matrix);
+        
+        for(int i = 0; i < row; i++){
+            for(int j = 0; j < col; j++){
+                if(matrix.get(i).get(j) == 1){
+                    helper (matrix, 1, i, j);
+                }
+            }
+        }
+        return matirx;
+    }
+}
+public void preSet(List<List<Integer>> matrix){
+    for (int i = 0; i < row; i++){
+        for (int j = 0; j < col; j++){
+            
+            if(matrix.get(i).get(j)==0){
+                continue;
+            }
+            
+            boolean flag = false;
+            for (int k = 0; k < 4; k++){
+                int x = i + dx[k];
+                int y = j + dy[k];
+                if (x < 0 || x >= row || y < 0 || y >= col){
+                    continue;
+                }
+                flag |= matrix.get(x).get(y) == 0;
+            }
+            if(!flag){
+                matrix.get(i).set(j, Integer.MAX_VALUE);
+            }
+                
+        }
+    }
+}
+
+public void helper (List<List<Integer>> matrix, int dist, int x, int y){
+    if (matrix.get(x).get(y) < dist){
+        return;
+    }
+    if(matrix.get(x).get(y) == dist && matrix.get(x).get(y) != 1){
+        return;
+    }
+    matrix.get(x).set(y, dist);
+    
+    for(int i = 0; i < 4; i++){
+        int xNext = x + dx[i];
+        int yNext = y + dy[i];
+        if(xNext < 0 || xNext >= row || yNext < 0 || yNext >= col ){
+            continue;
+        }
+        helper(matrix, dist + 1, xNext, yNext);
+    }
+ }