每日一题：组合总和 II

题意

给定一个候选人编号的集合 candidates 和一个目标数 target ，找出 candidates 中所有可以使数字和为 target 的组合。

candidates 中的每个数字在每个组合中只能使用 一次 。

示例 1:

输入: candidates = [10,1,2,7,6,1,5], target = 8,
输出:
    [
    [1,1,6],
    [1,2,5],
    [1,7],
    [2,6]
    ]

示例 2:

输入: candidates = [2,5,2,1,2], target = 5,
输出:
    [
    [1,2,2],
    [5]
    ]

提示:

• 1 <= candidates.length <= 100
• 1 <= candidates[i] <= 50
• 1 <= target <= 30

思想

代码实现

/**
 * @param {number[]} candidates
 * @param {number} target
 * @return {number[][]}
 */
var combinationSum2 = function (candidates, target) {
    let res = [], path = [], start_idx = 0, sum = 0,used =[]
    //排序
    candidates = candidates.sort((a, b) => a - b)

    backstracking(candidates, target, res, path, start_idx, sum,used)
    return res
};

let backstracking = (candidates, target, res, path, start_idx, sum,used) => {
    if (sum === target) {
        res.push(path.slice())
        return
    }
    if (sum > target) return
    for (let i = start_idx; i < candidates.length && sum <= target; i++) {
    
        if(i>0&&candidates[i]===candidates[i-1]&&!used[i-1]) continue

        path.push(candidates[i])
        sum += candidates[i]
        used[i] = true
        backstracking(candidates, target, res, path, i + 1, sum,used)
        sum -= candidates[i]
        used[i] = false
        path.pop()
    }
}