Equal Row and Column Pairs LeetCode solution in Java

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class Solution {
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  public int equalPairs(int[][] grid) {
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    HashMap<String, Integer> map = new HashMap<>();
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    int row = grid.length;
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    int col = grid.length;
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    for (int i = 0; i < row; i++) {
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      String res = "";
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      for (int j = 0; j < col; j++) {
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        res += "-" + grid[i][j];
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      }
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      map.put(res, map.getOrDefault(res, 0) + 1);
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    }
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    int cnt = 0;
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    for (int j = 0; j < col; j++) {
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      String res = "";
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      for (int i = 0; i < row; i++) {
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        res += "-" + grid[i][j];
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      }
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      cnt += map.getOrDefault(res, 0);
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    }
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    return cnt;
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  }
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}