Description

tag: array , backtraking

difficulty : medium

Given a collection of candidate numbers (candidates) and a target number (target), find all unique combinations in candidates where the candidate numbers sums to target.Each number in candidates may only be used once in the combination.Note:All numbers (including target) will be positive integers.The solution set must not contain duplicate combinations.Example 1:Input: candidates = [10,1,2,7,6,1,5], target = 8,A solution set is:[  [1, 7],  [1, 2, 5],  [2, 6],  [1, 1, 6]]Example 2:Input: candidates = [2,5,2,1,2], target = 5,A solution set is:[  [1,2,2],  [5]]

Solution

var results [][]intvar existed map[string]intfunc combinationSum2(candidates []int, target int) [][]int {    results = make([][]int, 0)    if len(candidates) == 0 {        return results    }    existed = make(map[string]int)    sort.Ints(candidates)    backtrack(candidates, target, nil)    return results}func backtrack(candidates []int, target int, result []int){    for i, val := range candidates {        if val == target {            result = append(result, val)            temp := make([]int, len(result))            copy(temp, result)            addIfNotExist(temp)            break        }        if val < target {            result = append(result, val)            backtrack(candidates[i+1:], target - val, result)            result = result[:len(result)-1]        }        if val > target {            break        }    }}func addIfNotExist(cr []int){    sort.Ints(cr)    var s string = ""    for _, val := range cr {        s += "," + string(val)    }    if _,ok := existed[s];ok {        return    }    results = append(results, cr)    existed[s] = 1}

Note:

• almost same with 39
• element can be used only once