UVA-1611 Crane (construction)

The main idea: to give a sequence of 1~n, each operation can be the length of an even-numbered sequence to exchange the first half and the last half of the position. Find the steps to turn this sequence into ascending order.

Problem Analysis: Structural solution.

The code is as follows:

# include<iostream># include<cstdio># include<queue># include<cstring># include< Algorithm>using namespace Std;int a[10005],pos[10005],n;queue<int>l,r;void print (int ans) {printf ("%d\n",    ANS); while (!        L.empty ()) {printf ("%d%d\n", L.front (), R.front ());    L.pop (), R.pop ();    }}void change (int l,int r) {L.push (L), R.push (R);        for (int i=l,j=l+ (r-l)/2+1;j<=r;++i,++j) {pos[a[i]]=j,pos[a[j]]=i;    Swap (a[i],a[j]); }}void solve () {while (!    L.empty ()) L.pop (); while (!    R.empty ()) R.pop ();    int l=1,ans=0;                while (L<=n) {for (int i=l;i<=n;++i) {if (a[i]==i) {++l;            Continue            } ++ans;            int p=pos[i];            if (2*p-i-1<=n) change (i,2*p-i-1);                else{if ((p-i) &1) Change (i,p);            else change (i+1,p);        } if (a[i]==i)        ++l;        Break }} print (ANS);}    int main () {int T;    scanf ("%d", &t);        while (t--) {scanf ("%d", &n);            for (int i=1;i<=n;++i) {scanf ("%d", a+i);        Pos[a[i]]=i;    } solve (); } return 0;}

　　

UVA-1611 Crane (construction)