乱七八糟代码合集٩(๑>◡<๑)۶

1.全排列

#include<bits/stdc++.h>
using namespace std;
int n = 3;
bool hashtable[100] = {false};
int P[100] = {-1};
int count_num = 0;
void f(int index){
    if(index == n + 1){
        for (int i = 1; i <= n; i++){
            printf("%d ", P[i]);
        }
        count_num++;
        printf("
");
        return;
    }
    for (int x = 1; x <= n; x++){
        if (hashtable[x] == false){
            P[index] = x;
            hashtable[x] = true;
            f(index + 1);
            hashtable[x] = false;
        }
    }
}

int main(){
    f(1);

    printf("
count=%d", count_num);
    return 0;
}

2.八皇后-暴力 

#include<bits/stdc++.h>
using namespace std;
int n = 4;
int P[9] = {0};
int cntnum = 0;
bool tablehash[9] = {false};

void f(int index){
    if (index == n + 1){
        bool flag = true;
        for (int i = 1; i <= n; i++){
            for (int j = i + 1; j <= n; j++){
                if (abs(i - j) == abs(P[i] - P[j])){
                    flag = false;
                }
            }
        }
        if (flag){
            for (int k= 1; k <= n; k++){
                printf("%d ", P[k]);
            }
            printf("
");
            cntnum++;
        }
        return;
    }
    for (int i = 1; i <= n; i++){
        if (tablehash[i] == false){
            P[index] = i;
            tablehash[i] = true;
            f(index + 1);
            tablehash[i] = false;
        }
    }
}
int main(){
    f(1);
    printf("%d", cntnum);
    return 0;
}

3.八皇后-回溯

#include<bits/stdc++.h>
using namespace std;
int n = 9;
int P[30] = {0};
int cntnum = 0;
bool tablehash[30] = {false};

void f(int index){
    if (index == n + 1){
        cntnum++;
        for (int k = 1; k <= n; k++){
            printf("%d ", P[k]);
        }
        printf("
");
        return;
    }
    for (int i = 1; i <= n; i++){
        bool flag = true;
        if (tablehash[i] == false){//假如第i行没有皇后, 即放在第 i 行第 index 列
            for (int j = 1; j < index; j++){//遍历和以前的皇后是否合法
                if (abs(index - j) == abs(P[j] - i)){
                    flag = false;
                    break;
                }
            }
            if (flag){//目前可以在第i行第index列放入皇后
                P[index] = i;
                tablehash[i] = true;
                f(index + 1);
                tablehash[i] = false;
            }
        }
    }

}

int main(){
    f(1);
    //printf("%d", cntnum);
    printf("%d", cntnum);
    return 0;
}

（未完待续~）