# 259. 3Sum Smaller

Given an array of n integers nums and a 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`.

For example, given nums = `[-2, 0, 1, 3]`, and target = 2.

Return 2. Because there are two triplets which sums are less than 2:

```[-2, 0, 1]
[-2, 0, 3]
```

Could you solve it in O(n2) runtime?

```public int ThreeSumSmaller(int[] nums, int target) {
Array.Sort(nums);
var res =0;
int size = nums.Count();
for(int i =0;i< size;i++)
{
int num = nums[i];
int dif = target - num;
int left =i+1;
int right = size -1;
while(left<right)
{
if(nums[left]+nums[right] < dif)
{
res+=right-left;
left++;
}
else right--;
}
}
return res;
}```

## LeetCode 259. 3Sum Smaller （三数之和较小值） \$

Given an array of n integers nums and a 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. For example, given nums = [-2, 0, 1, 3], and target = 2. Retu

## Leetcode 259. 3Sum Smaller

1 class Solution(object): 2 def threeSumSmaller(self, nums, target): 3 """ 4 :type nums: List[int] 5 :type target: int 6 :rtype: int 7 """ 8 nums.sort() 9 n = len(nums) 10 ans = 0 11 12 for k in range(n): 13 i, j = k+1, n-1 1

## 3Sum Smaller

Given an array of n integers nums and a 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. For example, given nums = [-2, 0, 1, 3], and target = 2. Retu

## 3Sum Smaller 解答

Question Given an array of n integers nums and a 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. For example, given nums = [-2, 0, 1, 3], and target

## 3Sum Smaller -- LeetCode

Given an array of n integers nums and a 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. For example, given nums = [-2, 0, 1, 3], and target = 2. Retu

## 过中等难度题目.0310

.   8  String to Integer (atoi)    13.9% Medium   . 151 Reverse Words in a String      15.7% Medium     . 288 Unique Word Abbreviation      15.8% Medium     . 29 Divide Two Integers      16.0% Medium     . 166 Fraction to Recurring Decimal      17.

## Sum 类型题目总结

Sum类的题目一般这样: input: nums[], target output: satisfied arrays/ lists/ number 拿到题目,首先分析: 1. 是几个数的sum 2. sum是要求等于target还是小于还是大于还是closest 3. 返回的是原数组下标还是其他 对于这类题目,我们经常用双指针的方法.即排序后,左指针指向起点,右指针指向终点. 如果sum等于target,加入结果/总数目+1 如果sum大于target,右指针左移 如果sum小于target,