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class Solution {
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 public:
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  vector<vector<int>> generate(int numRows) {
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    vector<vector<int>> ans(numRows, vector<int>());
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    for (int i = 0; i < numRows; i++) {
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      for (int j = 0; j <= i; j++) {
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        if (j == 0 || j == i) {
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          ans[i].push_back(1);
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        } else {
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          ans[i].push_back(ans[i - 1][j - 1] + ans[i - 1][j]);
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        }
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      }
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    }
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    return ans;
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  }
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};