代码：
public class Solution {
/**
* @param A an integer array
* @return a long integer
*/
public long permutationIndex(int[] A) {
// Write your code here
long R=0;
int low[] = new int[A.length];
long weight[] = new long[A.length];
for(int i=A.length-1;i>=0;--i){
for(int j=i+1;j<A.length;++j)
if(A[j]<A[i])
++low[i];
weight[i] = (i>=A.length-2)?(A.length-1-i):weight[i+1]*(A.length-i-1);
R += weight[i]*low[i];
}
return R+1;
}
}
lintcode截图：
