“给定一个小点的输入，完整单步跟踪一遍。”是理解递归函数工作原理的不二法门！

C/C++ code

#include <iostream>#include <string>using namespace std;class Queen{    public:        Queen();        ~Queen();    private:        int result;        string queen[8];        int state[8];        void set(int,int);        bool check(int,int);        void print();};Queen::Queen(){    result = 0;    for(int i=0;i<8;i++){        queen[i] = "--------";    }    set(0,0);}Queen::~Queen(){}void Queen::set(int i,int j){    if(i==8){        result++;        print();        queen[7]="--------";        set(7,state[7]+1);    }    else if(j==8){        if(i==0)        {            cout<<"共"<<result<<"种放置方法!"<<endl;        }        else{            queen[i-1]="--------";            set(i-1,state[i-1]+1);        }    }    else if(check(i,j)){        queen[i][j]='+';        state[i]=j;        set(i+1,0);    }    else{        set(i,j+1);    }}bool Queen::check(int i,int j){    for(int c=0;c<i;c++){        if(state[c]==j||state[c]-j==c-i||state[c]-j==i-c){            return false;        }    }    return true;}void Queen::print(){    for(int i=0;i<8;i++){        cout<<queen[i]<<endl;    }    cout<<"======"<<endl;}int main(){    Queen my;    system("pause");    return 0;}