离散化模板

    scanf("%d",&P);    for (int i=0; i!=P; i++)    {        scanf("%d",&A[i]);        B[i]=A[i];    }    sort(B,B+P);    int size=unique(B,B+P)-B;    for (int i=0; i!=P; i++)        A[i]=lower_bound(B,B+size,A[i])-B;