feat: word search

Author: minji-go

word-search/minji-go.java

@@ -0,0 +1,47 @@
+/*
+    Problem: https://leetcode.com/problems/word-search/
+    Description: return true if word exists in the grid
+    Concept: Array, String, Backtracking, Matrix
+    Time Complexity: O(MN4ᵀ), Runtime 147ms
+    Space Complexity: O(MN), Memory 42.11MB
+*/
+class Solution {
+    public char[][] board;
+    public String word;
+    public boolean[][] visited;
+    public int n, m;
+
+    public boolean exist(char[][] board, String word) {
+        this.board = board;
+        this.word = word;
+        this.m = board.length;
+        this.n = board[0].length;
+        this.visited = new boolean[m][n];
+
+        for(int i=0; i<m; i++){
+            for(int j=0; j<n; j++){
+                if(word.charAt(0) != board[i][j]) continue;
+                if(wordExists(i, j, 1)) return true;
+            }
+        }
+        return false;
+    }
+
+    public int[] dr = new int[]{-1,1,0,0};
+    public int[] dc = new int[]{0,0,-1,1};
+    public boolean wordExists(int cr, int cc, int i){
+        if(i==word.length()) return true;
+
+        visited[cr][cc] = true;
+        for(int k=0; k<4; k++){
+            int nr = cr+dr[k];
+            int nc = cc+dc[k];
+            if(nr<0||nc<0||nr>m-1||nc>n-1||visited[nr][nc]) continue;
+            if(board[nr][nc]!=word.charAt(i)) continue;
+            if(wordExists(nr, nc, i+1)) return true;
+        }
+        visited[cr][cc] = false;
+
+        return false;
+    }
+}