算法(TS)：找出数组中和为sum的n个数

使用递归和回溯

function findSum(arr: number[],target:number,count:number):number[][] {
    if(arr.length === 0 || count <= 0) return []
    const answers: number[][] = []
    const current: number[] = []

    const backtrack = (start: number,sum: number,n: number) => {
        if(sum === 0 && n === 0) {
            answers.push([...current])
            return
        }

        for(let i = start; i < arr.length; i++) {
            if(arr[i] <= sum) {
                current.push(arr[i])
                backtrack(i + 1,sum-arr[i],n-1)
                current.pop()
            }
        }
    }

    backtrack(0,target,count)
    return answers

}