poj #3971:scales

题目描述：http://poj.org/problem?id=3971

第一次用数位dp，参见http://www.cnblogs.com/lvpengms/p/3926678.html

#include <stdio.h>#include <string.h>#define MAX_N 1000000int N, L, D, dp[MAX_N][2];char w[MAX_N];int main(){int t, i;scanf("%d", &t);while(t--){scanf("%d%d%d", &N, &L, &D);getchar();memset(w, 0, sizeof(w)); for(i = L-1; i >= 0; i--){scanf("%c", &w[i]);w[i] -= 48;}memset(dp, 0, sizeof(dp));if(w[0]){dp[0][0] = 1;dp[0][1] = 1;}else{dp[0][0] = 1;dp[0][1] = 0;}for(i = 1; i < N; i++){if(w[i]){dp[i][0] += dp[i-1][0];dp[i][0] %= D;dp[i][1] += dp[i-1][0];dp[i][1] %= D;dp[i][1] += dp[i-1][1];dp[i][1] %= D; }else{dp[i][0] += dp[i-1][0];dp[i][0] %= D;dp[i][0] += dp[i-1][1];dp[i][0] %= D;dp[i][1] += dp[i-1][1];dp[i][1] %= D;}}printf("%d\n", dp[N-1][0]);}return 0;}