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三数之和.cpp
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三数之和.cpp
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#include <iostream>
#include <vector>
#include <algorithm>
using std::cin;
using std::cout;
using std::endl;
using std::vector;
using std::sort;
int main()
{
int n(0), target(0);
vector<int> data;
int input(0);
int count(0);
cin >> n >> target;
for (int i(0); i < n; ++i)
{
cin >> input;
data.push_back(input);
}
sort(data.begin(), data.end());
for (int i(0); i < data.size(); ++i)
{
int left(i + 1), right(data.size() - 1); // 作为两个指针,头尾
int we_need(target - data[i]); // 作为left与right的需求,要求他们两个对应的元素加起来的值等于we_need
// cout << data[i] << " : " <<we_need << endl;
while (left < right) // 只要两个指针的位置是正常的,就可以继续进行这个循环
{
int now_sum(data[left] + data[right]);
// cout << data[left] << " " << data[right] << endl;
if (now_sum < we_need)
++left; // 因为需要更大的数据
else if (now_sum > we_need)
--right;
else
{
++count;
++left;
--right;
}
}
// cout << "?" << endl;
}
cout << "wo yi yue du guan yu chao xi de shuo ming" << endl;
cout << count;
return 0;
}