回溯法应用

题目

笔试的时候遇到这么一个问题：

6 = 1+1 +1+ 1+ 1 +1

6 = 1+ 1+ 1+ 1+ 2

6 = 1+ 1+ 1+ 3

6 = 1+ 1+ 2+ 2

6 = 1+ 1+ 4

6 = 1+ 2+ 3

6 = 1+ 5

6 = 2+ 2+ 2

6 = 2+ 4

6 = 3+ 3

6 = 6

就这样，给定一个数，打印出这种形式

分析

递归，回溯。

代码

[code]#include<iostream>
#include<vector>
using namespace std;

void print(int n, vector<int> &re){
    if(n < 0)
        return;
    if(n == 0){
        for(auto i : re){
            cout << i << " ";
        }
        cout << endl;
    }
    else{
        int start = 1;
        int length = re.size();
        if(length != 0)
            start = re.at(length - 1);
        for(int i = start; i <= n; i++){
            re.push_back(i);
            print(n - i, re);
            re.pop_back();
        }
    }
}
int main(){
    vector<int> re;
    print(6, re);
    return 0;
}