zoj 3823 Excavator Contest(结构体)

题目链接：zoj 3823 Excavator Contest

题目大意：一个人开着挖掘机要在N*N的格子上面移动。要求走全然部的格子。而且转完次数要至少为n*(n-1) - 1次，

而且终点和起点必须都在边界上。

解题思路：构造。由于终点和起点必须在边界上，进去的同一时候得留出一条路径出来。

• 奇数
  
  
• 偶数
  
  

奇数的情况分两种（图上两点所代表的正方形构造方式是一样的。即13。9为一类，11。7为一类）

偶数分为四类(图上两点所代表的正方形构造方式是不一样的，即14，12，10，8各为一类)

这是我做过最恶心的构造题了。

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

const int maxn = 550;
const int dir[4][2] = {{-1, 0}, {1, 0}, {0, -1}, {0, 1}};

//const int G[5][50] = {{0}, {0}, {3, 4, 2, 1}, {5, 6, 9, 4, 7, 8, 3, 2, 1}};

const int dir_down[4][4][4] = { {{3, 1, 2, 1}, {3, 3, 0, 3}, {1, 3, 0, 3}, {1, 3, 0, 0}},
    {{2, 1, 3, 1}, {2, 1, 3, 3}, {0, 3, 1, 3}, {3, 0, 2, 0}}, 
    {{3, 1, 2, 1}, {1, 3, 0, 3}, {1, 3, 0, 0}} };

const int dir_left[5][4] = { {1, 2, 0, 2}, {1, 2, 0, 2}, {2, 1, 3, 1}, {0, 2, 1, 2}, {0, 2, 1, 1}};
const int dir_up[5][4] = { {2, 0, 3, 0}, {2, 0, 3, 0}, {0, 2, 1, 2}, {3, 0, 2, 0}, {3, 0, 2, 2} };

int L, R, g[maxn][maxn];

void put(int n);

inline void jump(int n, int& x, int& y, int& mv, int len, const int d[4]) {
    for (int i = 0; i < n; i++) {
        for (int j = 0; j < 4; j++) {
            g[x][y] = mv;
            mv += len;
            x += dir[d[j]][0];
            y += dir[d[j]][1];
        }
    }
}

inline void moveup(int n, int& x, int& y, int& mv, int len) {
    //printf("moveup:%d
", len);
    if (n&1) {
        jump(n / 2 - 1, x, y, mv, len, dir_up[0]);
        for (int t = 0; t < 2; t++) {
            g[x][y] = mv;
            x += dir[2][0];
            y += dir[2][1];
            mv += len;
        }
    } else if ((n/2) % 4) {
        jump(n / 2 - 2, x, y, mv, len, dir_up[1]);
        jump(1, x, y, mv, len, dir_up[2]);
    } else {
        jump(n / 2 - 2, x, y, mv, len, dir_up[3]);
        jump(1, x, y, mv, len, dir_up[4]);
    }
}

inline void moveleft(int n, int& x, int& y, int& mv, int len) {
    //printf("moveleft:%d
", len);
    if (n&1) {
        jump(n / 2, x, y, mv, len, dir_left[0]);
        for (int t = 0; t < 2; t++) { // down twice;
            g[x][y] = mv;
            x += dir[1][0];
            y += dir[1][1];
            mv += len;
        }
    } else if ((n/2) % 4) {
        jump(n / 2 - 1, x, y, mv, len, dir_left[1]);
        jump(1, x, y, mv, len, dir_left[2]);
    } else {
        jump(n / 2 - 1, x, y, mv, len, dir_left[3]);
        jump(1, x, y, mv, len, dir_left[4]);
    }
}

inline void movedown(int n, int& x, int& y, int& mv, int len) {
    int p;

    //printf("movedown!
");
    if (n&1) {
        for (int k = 0; k < 4; k++) {
            if (k == 0) p = n / 2;
            else if (k == 1 || k == 3) p = 1;
            else p = n / 2 - 2;
            jump(p, x, y, mv, len, dir_down[0][k]);
        }
    } else if ((n/2) % 4 == 1) {
        for (int k = 0; k < 4; k++) {
            if (k == 0) p = n / 2 - 1;
            else if (k == 1 || k == 3) p = (n == 2 && k == 3 ?
 0 : 1);
            else p = max(n / 2 - 2, 0);
            jump(p, x, y, mv, len, dir_down[1][k]);
        }
    } else {
        for (int k = 0; k < 3; k++) {
            if (k == 0 || k == 1) p = n / 2 - 1;
            else p = 1;
            jump(p, x, y, mv, len, dir_down[2][k]);
        }
    }
}

void solve (int n, int sx, int sy, int ex, int ey, int flag) {
    if (n <= 1) {
        if (n == 1)
            g[sx][sy] = L;
        return;
    } 

    /*
    printf("%d:
", n);
    put(10);
    */

    if (n&1) {
        if ((n/2)&1) {
            if (flag) {
                moveup(n, sx, sy, L, 1);
                moveleft(n, ex, ey, R, -1);
            } else {
                moveup(n, ex, ey, R, -1);
                moveleft(n, sx, sy, L, 1);
            }
            solve(n - 2, sx, sy, ex, ey, flag);
        } else {
            if (flag)
                movedown(n, ex, ey, R, -1);
            else 
                movedown(n, sx, sy, L, 1);
            solve(n - 2, sx, sy, ex, ey, flag^1);
        }
    } else {
        if ((n/2)&1) {
            if (flag)
                movedown(n, ex, ey, R, -1);
            else
                movedown(n, sx, sy, L, 1);
            solve(n - 2, sx, sy, ex, ey, flag^1);
        } else {
            if (flag) {
                moveup(n, sx, sy, L, 1);
                moveleft(n, ex, ey, R, -1);
            } else {
                moveup(n, ex, ey, R, -1);
                moveleft(n, sx, sy, L, 1);
            }
            solve(n - 2, sx, sy, ex, ey, flag);
        }
    }
}

void put (int n) {
    for (int i = 1; i <= n; i++) {
        printf("%d", g[i][1]);
        for (int j = 2; j <= n; j++)
            printf(" %d", g[i][j]);
        printf("
");
    }
}

int main () {
    int cas, n;
    scanf("%d", &cas);
    while (cas--) {
        scanf("%d", &n);

        int sx, sy, ex, ey, flag;
        L = 1, R = n * n;

        if (n&1) {
            if ((n/2)&1)
                ex = 1, ey = sx = sy = n, flag = 1;
            else
                sx = sy = ex = 1, ey = n, flag = 0;
        } else {
            int t = n / 2;
            t = (t - 1) % 4 + 1;
            if (t == 1)
                sx = 1, sy = ex = 2, ey = n, flag = 0;
            else if (t == 2)
                sx = sy = ey = n, ex = 1, flag = 1;
            else if (t == 3)
                sx = sy = ex = 1, ey = n, flag = 0;
            else
                sx = ey = n, sy = n - 1, ex = 2, flag = 1;
        }

        //printf("%d %d %d %d %d!!!
", sx, sy, ex, ey, flag);
        solve(n, sx, sy, ex, ey, flag);
        put(n);
    }
    return 0;
}

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