回溯加剪枝。只需DFS右、下两个方向即可，可以一行一行来。弄完一行之后看下该行所有数字是否都配对了，否则剪枝。还是得细心，两个 cnt 认错了找了大半天 bug 。。。

#include
    
     using namespace std;const int n = 7;int cnt;int dx[] = {1, 0}, dy[] = {0, 1};int dict[n][n], G[n][n+1], M[n][n+1], vis[n][n+1], use[30];bool judge(int x) {    for (int j = 0; j <= n; j++)        if (vis[x][j] == 0) return true;    return false;}void DFS(int x, int y, int cnt2){    if(cnt2 == 28){        for(int i = 0; i < n; i++){            for(int j = 0; j <= n; j++){                printf("%4d", M[i][j]);            }            putchar('\n');        }        putchar('\n');        cnt++;        return;    }    if(x == n) return;    if(y == n+1){        if (judge(x)) return;        DFS(x + 1, 0, cnt2);        return;    }    if(vis[x][y]){        DFS(x, y + 1, cnt2);        return;    }    for(int i = 0; i < 2; i++){        int nx = x + dx[i], ny = y + dy[i];        int k = dict[G[x][y]][G[nx][ny]];        if(nx == n || ny == n+1 || vis[nx][ny] || use[k]) continue;        M[x][y] = M[nx][ny] = k;        vis[x][y] = vis[nx][ny] = use[k] = 1;        DFS(x, y + 1, cnt2 + 1);        vis[x][y] = vis[nx][ny] = use[k] = 0;    }}int main(){    // freopen("data.in","r",stdin);    // freopen("data.out","w",stdout);    int c = 1;    for(int i = 0; i < n; i++)        for(int j = i; j < n; j++)            dict[j][i] = dict[i][j] = c++;    int T = 0;    while(scanf("%d", &G[0][0]) != EOF){        for(int i = 0; i < n; i++){            for(int j = 0; j <= n; j++){                if(!i && !j) continue;                scanf("%d", &G[i][j]);            }        }        if(T++) printf("\n\n\n");        printf("Layout #%d:\n\n", T);        for(int i = 0; i < n; i++){            for(int j = 0; j <= n; j++){                printf("%4d", G[i][j]);            }            putchar('\n');        }        printf("\nMaps resulting from layout #%d are:\n\n", T);        cnt = 0;        DFS(0, 0, 0);        printf("There are %d solution(s) for layout #%d.\n", cnt, T);    }    return 0;}