LeetCode - 16. 3Sum Closest
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16. 3Sum Closest
Problem‘s Link
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Mean:
给定一个整数序列和一个目标数,在序列中找出三个数,使得这三个数的和与目标数的差最小.
analyse:
O(n^2)的做法.
如果你找到了更好的做法,请赐教^_^
Time complexity: O(N)
view code
/**
* -----------------------------------------------------------------
* Copyright (c) 2016 crazyacking.All rights reserved.
* -----------------------------------------------------------------
* Author: crazyacking
* Date : 2016-02-17-08.50
*/
#include <queue>
#include <cstdio>
#include <set>
#include <string>
#include <stack>
#include <cmath>
#include <climits>
#include <map>
#include <cstdlib>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
using namespace std;
typedef long long(LL);
typedef unsigned long long(ULL);
const double eps(1e-8);
class Solution
{
public:
int threeSumClosest(vector<int>& nums, int target)
{
int si=nums.size();
if(si<3) return 0;
if(si==3) return (nums[0]+nums[1]+nums[2]);
int64_t res=INT_MAX,low,high,sum,tsum;
sort(nums.begin(),nums.end());
for(int i=0;i<si;++i)
{
low=i+1;
high=si-1;
tsum=target-nums[i];
while(low<high)
{
sum=(nums[i]+nums[low]+nums[high]);
if(abs(target-res)>abs(target-sum))
res=sum;
if(nums[low]+nums[high]<tsum)
++low;
else if(nums[low]+nums[high]>tsum)
--high;
else
return target;
}
}
return (int)res;
}
};
int main()
{
Solution solution;
int n,target;
while(cin>>n>>target)
{
vector<int> ve;
for(int i=0;i<n;++i)
{
int tmp;
cin>>tmp;
ve.push_back(tmp);
}
int ans=solution.threeSumClosest(ve,target);
cout<<ans<<endl;
}
return 0;
}
* -----------------------------------------------------------------
* Copyright (c) 2016 crazyacking.All rights reserved.
* -----------------------------------------------------------------
* Author: crazyacking
* Date : 2016-02-17-08.50
*/
#include <queue>
#include <cstdio>
#include <set>
#include <string>
#include <stack>
#include <cmath>
#include <climits>
#include <map>
#include <cstdlib>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
using namespace std;
typedef long long(LL);
typedef unsigned long long(ULL);
const double eps(1e-8);
class Solution
{
public:
int threeSumClosest(vector<int>& nums, int target)
{
int si=nums.size();
if(si<3) return 0;
if(si==3) return (nums[0]+nums[1]+nums[2]);
int64_t res=INT_MAX,low,high,sum,tsum;
sort(nums.begin(),nums.end());
for(int i=0;i<si;++i)
{
low=i+1;
high=si-1;
tsum=target-nums[i];
while(low<high)
{
sum=(nums[i]+nums[low]+nums[high]);
if(abs(target-res)>abs(target-sum))
res=sum;
if(nums[low]+nums[high]<tsum)
++low;
else if(nums[low]+nums[high]>tsum)
--high;
else
return target;
}
}
return (int)res;
}
};
int main()
{
Solution solution;
int n,target;
while(cin>>n>>target)
{
vector<int> ve;
for(int i=0;i<n;++i)
{
int tmp;
cin>>tmp;
ve.push_back(tmp);
}
int ans=solution.threeSumClosest(ve,target);
cout<<ans<<endl;
}
return 0;
}
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