Given an array of n integers nums and an integer target, find the number of index triplets i, j, k with 0 <= i < j < k < n that satisfy the condition nums[i] + nums[j] + nums[k] < target.
Follow up: Could you solve it in O(n2) runtime?
Example 1:
Input: nums = [-2,0,1,3], target = 2 Output: 2 Explanation: Because there are two triplets which sums are less than 2: [-2,0,1] [-2,0,3]
Example 2:
Input: nums = [], target = 0 Output: 0
Example 3:
Input: nums = [0], target = 0 Output: 0
题意
三数之和小于target的个数
思路
K Sum 模板
代码
public int threeSumSmaller(int[] nums, int target) {
if (nums == null || nums.length == 0) return 0;
int result = 0;
Arrays.sort(nums);
for (int i = 0; i < nums.length - 2; i++) {
int j = i + 1;
int k = nums.length - 1;
while (j < k) {
int sum = nums[i] + nums[j] + nums[k];
if (sum < target) {
result += k - j;
j++;
} else {
k--;
}
}
}
return result;
}