Minimum Path Cost in a Grid LeetCode solution in Java

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class Solution {
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  Integer dp[][];
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  public int minPathCost(int[][] grid, int[][] moveCost) {
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    dp = new Integer[grid.length][grid[0].length];
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    int ans = Integer.MAX_VALUE;
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    for (int i = 0; i < grid[0].length; i++) {
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      ans = Math.min(ans, grid[0][i] + helper(grid, moveCost, grid[0][i], 1));
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    }
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    return ans;
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  }
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  public int helper(int[][] grid, int[][] moveCost, int cur, int i) {
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    if (i == grid.length) {
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      return 0;
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    }
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    int ans = Integer.MAX_VALUE;
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    for (int k = 0; k < grid[0].length; k++) {
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      int a = Integer.MAX_VALUE;
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      if (dp[i][k] != null) {
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        a = dp[i][k];
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      } else {
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        a = helper(grid, moveCost, grid[i][k], i + 1);
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        dp[i][k] = a;
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      }
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      ans = Math.min(grid[i][k] + moveCost[cur][k] + a, ans);
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    }
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    return ans;
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  }
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}