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class Solution {
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 public
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  int triangleNumber(int[] nums) {
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    int n = nums.length;
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    Arrays.sort(nums);
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    int count = 0;
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    for (int k = n - 1; k >= 2; k--) {
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      int i = 0;
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      int j = k - 1;
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      while (i < j) {
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        int sum = nums[i] + nums[j];
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        if (sum > nums[k]) {
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          count += j - i;
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          j--;
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        } else {
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          i++;
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        }
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      }
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    }
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    return count;
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  }
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}