寻找一个图中独立子图的个数

#include <stdio.h>

int map[51][51] =
{
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 1, 2, 1, 0, 0, 0, 0, 0, 2, 3},
{0, 3, 0, 2, 0, 1, 2, 1, 0, 1, 2},
{0, 4, 0, 1, 0, 1, 2, 3, 2, 0, 1},
{0, 3, 2, 0, 0, 0, 1, 2, 4, 0, 0},
{0, 0, 0, 0, 0, 0, 0, 1, 5, 3, 0},
{0, 0, 1, 2, 1, 0, 1, 5, 4, 3, 0},
{0, 0, 1, 2, 3, 1, 3, 6, 2, 1, 0},
{0, 0, 0, 3, 4, 8, 9, 7, 5, 0, 0},
{0, 0, 0, 0, 3, 7, 8, 6, 0, 1, 2},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0}
};
int book[51][51] = {0};
int sum = 0;
int next[4][2] = {{0, 1}, {1, 0}, {0, -1}, {-1, 0}};
void dfs(int x, int y,int color)
{
int k;
int tx, ty;
map[x][y] = color;
for (k = 0; k <= 3; k++)
{
tx = x + next[k][0];
ty = y + next[k][1];

if (tx < 1 || tx > 10 || ty < 1 || ty > 10)
continue;

if (map[tx][ty] > 0 && book[tx][ty] == 0)
{
sum++;
book[tx][ty] = 1;
dfs(tx, ty, color);
//book[tx][ty] = 0;
}
}
return;
}
int main()
{
int i,j;
int num = 0;

//
for (i = 1; i <= 10; i++)
for (j = 1; j <= 10; j++)
{
if (map[i][j] > 0)
{
num--;
book[i][j] = 1;
dfs(i, j, num);
}
}

for (i = 1; i <= 10; i++)
{
for (j = 1; j <= 10; j++)
{
printf("%3d ", map[i][j]);
}
printf("\n");
}
printf("小岛总共有%d个小岛\n",-num);
getchar();
getchar();
return 0;
}