hdu 2151 Worm（Easy DP）

#include <queue>
#include <stack>
#include <math.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <limits.h>
#include <string.h>
#include <string>
#include <algorithm>
#define MID(x,y) ( ( x + y ) >> 1 )
#define L(x) ( x << 1 )
#define R(x) ( x << 1 | 1 )
#define BUG puts("here!!!")

using namespace std;

const int MAX = 110;
int dp[MAX][MAX];

int main()
{
	int n,p,m,t;
	
	while( ~scanf("%d%d%d%d",&n, &p, &m, &t) )
	{
		memset(dp, 0, sizeof(dp));
		
		if( p <= n-1 ) dp[1][p+1] = 1;
		if( p >= 2 ) dp[1][p-1] = 1;
		for(int i=2; i<=m; i++)
			for(int k=1; k<=n; k++)
				dp[i][k] += (dp[i-1][k-1] + dp[i-1][k+1]);
		
		int ans = dp[m][t];
		printf("%d\n",ans);
	}

return 0;
}