<\/p>\n
2 seconds<\/p><\/div>\n
256 megabytes<\/p><\/div>\n
standard input<\/p><\/div>\n
standard output<\/p><\/div>\n<\/div>\n
Petya and Vasya are playing a game. Petya’s got\u00a0n<\/i>\u00a0non-transparent glasses, standing in a row. The glasses’ positions are indexed with integers from\u00a01\u00a0to\u00a0n<\/i>\u00a0from left to right. Note that the positions are indexed but the glasses are not.<\/p>\n
First Petya puts a marble under the glass in position\u00a0s<\/i>. Then he performs some (possibly zero) shuffling operations. One shuffling operation means moving the glass from the first position to position\u00a0p<\/i>1<\/sub>, the glass from the second position to position\u00a0p<\/i>2<\/sub>\u00a0and so on. That is, a glass goes from position\u00a0i<\/i>\u00a0to position\u00a0p<\/i>i<\/i><\/sub>. Consider all glasses are moving simultaneously during one shuffling operation. When the glasses are shuffled, the marble doesn’t travel from one glass to another: it moves together with the glass it was initially been put in.<\/p>\n After all shuffling operations Petya shows Vasya that the ball has moved to position\u00a0t<\/i>. Vasya’s task is to say what minimum number of shuffling operations Petya has performed or determine that Petya has made a mistake and the marble could not have got from position\u00a0s<\/i>to position\u00a0t<\/i>.<\/p>\n<\/div>\n The first line contains three integers:\u00a0n<\/i>,\u2009s<\/i>,\u2009t<\/i>\u00a0(1\u2009\u2264\u2009n<\/i>\u2009\u2264\u2009105<\/sup>;\u00a01\u2009\u2264\u2009s<\/i>,\u2009t<\/i>\u2009\u2264\u2009n<\/i>)\u00a0\u2014 the number of glasses, the ball’s initial and final position. The second line contains\u00a0n<\/i>\u00a0space-separated integers:\u00a0p<\/i>1<\/sub>,\u2009p<\/i>2<\/sub>,\u2009…,\u2009p<\/i>n<\/i><\/sub>\u00a0(1\u2009\u2264\u2009p<\/i>i<\/i><\/sub>\u2009\u2264\u2009n<\/i>)\u00a0\u2014 the shuffling operation parameters. It is guaranteed that all\u00a0p<\/i>i<\/i><\/sub>‘s are distinct.<\/p>\n Note that\u00a0s<\/i>\u00a0can equal\u00a0t<\/i>.<\/p>\n<\/div>\n If the marble can move from position\u00a0s<\/i>\u00a0to position\u00a0t<\/i>, then print on a single line a non-negative integer \u2014 the minimum number of shuffling operations, needed to get the marble to position\u00a0t<\/i>. If it is impossible, print number -1.<\/p>\n<\/div>\n B. Find Marble time limit per tes … \u7d9a\u304d\u3092\u8aad\u3080 4 2 1 2 3 4 1<\/pre>\n<\/div>\n
3<\/pre>\n<\/div>\n
4 3 3 4 1 3 2<\/pre>\n<\/div>\n
0<\/pre>\n<\/div>\n
4 3 4 1 2 3 4<\/pre>\n<\/div>\n
-1<\/pre>\n<\/div>\n
3 1 3 2 1 3<\/pre>\n<\/div>\n
-1<\/pre>\n<\/div>\n<\/div>\n<\/div>\n
\r\n#include <iostream>\r\n#include <cstdio>\r\n#include <cstring>\r\n\r\nusing namespace std;\r\n\r\nint a[100005];\r\nint b[100005];\r\n\r\nint main()\r\n{\r\n int n,s,t,tmp,ans=0,err=0;\r\n cin>>n>>s>>t;\r\n for(int i=1;i<=n;i++)\r\n cin>>a[i];\r\n tmp=s;\r\n while(t!=tmp)\r\n {\r\n if(b[tmp])\r\n {\r\n err=1;\r\n t++;\r\n cout\r\n break;\r\n }\r\n b[tmp]=1;\r\n tmp=a[tmp];\r\n ans++;\r\n }\r\n if(err)cout<<-1<<endl;\r\n else cout<<ans<<endl;\r\n return 0;\r\n}\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"