leetcode-题7--sum

非暴力不合作；深度优先

#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;

void dfs(const vector<int>&a,int ind1,int ind2,int tar,vector<int>&path)
{
    if (a[ind1 - 1] + a[ind2 - 1] == tar)
    {
        path.push_back(ind1);
        path.push_back(ind2);
        return;
    }
    if (ind1 == ind2)return;
    dfs(a, ind1 + 1, ind2, tar, path);
    dfs(a, ind1, ind2 - 1, tar, path);
}

int main()
{
    int a[4] = { 2,3,11,15 };
    vector<int>nums(a, a + 4);
    vector<int>path;
    dfs(nums, 1, 4, 13, path);
    for (auto i : path)
        cout << i << endl;
    system("pause");
    return 0;
}

解法2：

网上炒的跪服：

#include <iostream>
#include <algorithm>
#include <unordered_map>

using namespace std;

int main()
{
    int a[4] = { 2,3,11,15 };
    unordered_map<int, int>nums;
    for (int i = 0; i < 4; ++i)
        nums[a[i]] = i;
    int tar;
    cin >> tar;
    for (int i = 0; i < 4; ++i)
    {
        int tem = tar - a[i];
        if (nums.find(tem) != nums.end())
        {
            int k = nums[tem];
            if (k != i)
                cout << i+1 << ' ' << k+1 << endl;
            break;
        }
    }
    system("pause");
    return 0;
}