1，暴力法
C++：
class Solution {
public:
int threeSumClosest(vector<int>& nums, int target) {
if ( nums.size() < 3 ) {
return 0;
}
int closedTarget = nums[0] + nums[1] + nums[2];
for ( int i = 0; i <= nums.size() - 3; ++i ) {
for ( int j = i + 1; j <= nums.size() - 2; ++j ) {
for ( int k = j + 1; k <= nums.size() - 1; ++k ) {
int sum = nums[i] + nums[j] + nums[k];
if ( abs( sum - target ) < abs( closedTarget - target ) ) {
closedTarget = sum;
}
}
}
}
return closedTarget;
}
};
2，排序 + 双指针
C++：
class Solution {
public:
int threeSumClosest(vector<int>& nums, int target) {
if ( nums.size() < 3 ) {
return 0;
}
std::sort(nums.begin(), nums.end());
int result = nums[0] + nums[1] + nums[2];
for ( int i = 0; i < nums.size(); ++i ) {
int left = i + 1;
int right = nums.size() - 1;
while ( left < right ) {
int sum = nums[i] + nums[left] + nums[right];
if ( sum == target ) {
return target;
}
if ( sum > target ) {
--right;
} else {
++left;
}
if ( abs( sum - target ) < abs( result - target ) ) {
result = sum;
}
}
}
return result;
}
};
