poj 1322 Chocolate

#include <iostream>#include <stdio.h>#include <string.h>using namespace std;double dp[2][102];int main(){int c, n, m, i, j;while(scanf("%d", &c) && c){scanf("%d %d", &n, &m);if(m > n || m > c || (m + n) % 2){    printf("0.000n");continue;}if(n > 1001)n = n % 2 ? 1001 : 1000;memset(dp, 0, sizeof(dp));        dp[0][0] = 1.0;        for(i = 1; i <= n; i++){for(j = 0; j <= i && j <= c; j++){dp[i%2][j] = 0.0;if((i + j) % 2) continue;if(j > 0)        dp[i%2][j] += dp[1-i%2][j-1] * ((c-j+1.0)*1.0/c);if(j+1 <= i-1)dp[i%2][j] += dp[1-i%2][j+1] * ((j+1.0)*1.0/c);}}printf("%.3lfn", dp[n%2][m]);}return 0;}