如果返回数字而不是布尔值，则可以区分存在0、1或多于1个解决方案的情况。
// returns 0, 1 or more than 1 depending on whether 0, 1 or more than 1 solutions are foundstatic byte solve(int i, int j, int[][] cells, byte count ) { if (i == 9) { i = 0; if (++j == 9) return 1+count; } if (cells[i][j] != 0) // skip filled cells return solve(i+1,j,cells, count); // search for 2 solutions instead of 1 // break, if 2 solutions are found for (int val = 1; val <= 9 && count < 2; ++val) { if (legal(i,j,val,cells)) { cells[i][j] = val; // add additional solutions count = solve(i+1,j,cells, count)); } } cells[i][j] = 0; // reset on backtrack return count;}
