C :

#include<stdio.h>
#include<string.h>
int main()
{
	int n,i,j,x[21],y[21],flag;
	char str[100];
	while(1)
	{
		scanf("%d",&n);
		if(n==0) break;
		for(i=1;i<=20;i++)
		{
			x[i]=25;
			y[i]=31-i;
		}
		scanf("%s",&str);
		for(flag=0,i=0;i<n;i++)
		{
			for(j=20;j>1;j--) {x[j]=x[j-1];y[j]=y[j-1];}
			if(str[i]=='E') y[1]+=1;
			if(str[i]=='S') x[1]+=1;
			if(str[i]=='W') y[1]-=1;
			if(str[i]=='N') x[1]-=1;
			if(x[1]<1||x[1]>50||y[1]<1||y[1]>50) flag=1;
			for(j=20;j>1;j--) 
				if(x[j]==x[1]&&y[j]==y[1])
				{
					flag=2;
					break;
				}
			if(flag==1) 
			{
				printf("The worm ran off the board on move %d.\n",i+1);
				break;
			}
			if(flag==2)
			{
				printf("The worm ran into itself on move %d.\n",i+1);
				break;
			}
		}
		if(flag==0) printf("The worm successfully made all %d moves.\n",n);
	}
	return 0;
}

C++ :

#include <cstdio>
#include <vector>
#include <deque>
#include <algorithm>
using namespace std;

const int ix[4] = {-1, 0, 1, 0};
const int iy[4] = {0, 1, 0, -1};
int dir[300];

void solve(char *s, int m) {
    static int n = 50;
    vector < vector < bool > > data(n, vector < bool >(n));
    fill(data[24].begin() + 10, data[24].begin() + 30, true);
    deque < int > q;
    for (int y = 10; y < 30; ++y)
        q.push_back(2400 + y);
    for (int i = 1; i <= m; ++i) {
        int k = dir[ s[i - 1] ];
        int x = q.back() / 100, y = q.back() % 100;
        int nx = x + ix[k], ny = y + iy[k];
        if (nx < 0 || nx >= n || ny < 0 || ny >= n) {
            printf("The worm ran off the board on move %d.\n", i);
            return;
        }
        data[q.front() / 100][q.front() % 100] = false;
        if (data[nx][ny]) {
            printf("The worm ran into itself on move %d.\n", i);
            return;
        }
        data[nx][ny] = true;
        q.pop_front();
        q.push_back(nx * 100 + ny);
    }
    printf("The worm successfully made all %d moves.\n", m);
}

int main() {
    dir['N'] = 0;
    dir['E'] = 1;
    dir['S'] = 2;
    dir['W'] = 3;
    char str[205];
    int n;
    while (scanf("%d", &n) && n > 0) {
        scanf("%s", str);
        solve(str, n);
    }
    return 0;
}

Java :

import java.util.*;
public class Main {
	static int[][] map=null;
	static int n=0;
	static String str=null;
	static char c;
	static int headx;
	static int heady;
	static int tailx;
	static int taily;
	static int step;
	public static void main(String[] args) {
		Scanner in=new Scanner(System.in);
		
		while(in.hasNext()){
			n=Integer.parseInt(in.nextLine());
			if(n==0){
				break;
			}
			str=in.nextLine();
			map=new int[50][50];
			step=0;
			//初始化地图
			for(int i=10;i<=29;i++){
				map[24][i]=1;
			}
			headx=24;
		    heady=29;
			tailx=24;
			taily=10;
			//
			int num=move();
			 if (num == 1)
                 System.out.println("The worm ran into itself on move "+step+".");
			 	else if (num == 2)
			 			System.out.println("The worm ran off the board on move "+step+".");
			 			else
			 				System.out.println("The worm successfully made all "+step+" moves.");
			
			}
			
			
		}
		
	
	public static int move(){
		
		for(int i=0;i<n;i++){
			 step=i+1;
			c=str.charAt(i);
			//
			switch(c){
			case 'W':
				heady--;
				break;
			case 'E':
				heady++;
				break;
			case 'S':
				headx--;
				break;
			case 'N':
				headx++;
				break;
			}
           map[tailx][taily]=0;
			if (headx >= 50 || headx < 0 || heady >=50 || heady < 0 || tailx>=50 || tailx < 0 || taily >=50 || taily < 0)
            return 2;
			if (map[headx][heady]==1)
                return 1;
			map[headx][heady]=1;
			
			 if (step <= 19)
                 taily++;
         else {
                 switch (str.charAt(step - 20)) {
                 case 'E':
                         taily++;
                         break;
                 case 'W':
                         taily--;
                         break;
                 case 'N':
                         tailx--;
                         break;
                 case 'S':
                         tailx++;
                         break;
                 }
         }
			
	}
		return 3;
}
}