这道题我不清楚跟N-Queens的区别是什么,核心算法都是一样的,只是这道题是计数,前一道是计算具体的组合,组合都出来了,计数还会难吗?不bb,上代码:
public class Solution { public int totalNQueens(int n) { Map<Integer,Integer> result = new HashMap<>(); int[] q=new int[n]; for(int i = 0 ; i<n; i++){ enumerate(result, i, q, 0); } if(result.get(1)==null){ return 0; } return result.get(1); } public boolean isConsistent(int[] q, int line, int index){ if(line==0){ return true; }else{ for(int i=0; i<line;i++){ //i行q[i]列 vs line行index列 if(q[i]==index){ //同列 return false; } if(index-q[i]==line-i){ return false; } if(index-q[i]==i-line){ return false; } } return true; } } public void enumerate(Map<Integer,Integer> result, int index, int[] q, int line){ if(line==q.length-1){ if(isConsistent(q, line, index)){ q[line] = index; if(result.get(1)==null){ result.put(1,1); }else{ result.put(1,result.get(1)+1); } } }else if(line == 0){ q[line] = index; for(int j = 0; j<q.length; j++){ enumerate(result, j, q, line+1); } }else{ if(isConsistent(q, line, index)){ q[line] = index; for(int j = 0; j<q.length; j++){ enumerate(result, j, q, line+1); } } } } }