SOURCE

> [[7,8],[9,6],[8,7],[10,5],[13,2],[14,1]]

// 求和问题，给定数组，求和是N的两个数组合

function sumN (N, nums) {
    let answers = [], tmpDic = {}
    for(let index in nums) {
        if(nums[index] < N) {
            if(tmpDic[nums[index]]) tmpDic[nums[index]] ++
            else tmpDic[nums[index]] = 1
            
            let key = N - nums[index]
            if(tmpDic[key] == 1) {
                answers.push([nums[index], key])
            }
        }
    }
    console.log(answers)
}

sumN(15, [8, 7, 2, 4, 6, 9, 1, 5, 8, 3, 10, 4, 11, 13, 14])