codeforces 进制01问题

题目连接：http://codeforces.com/problemset/problem/165/C

题目看起来很难，反正我是被吓坏了

题目代码：

#include<iostream>#include<cstdio>#include<cstring>#include<string>#include<algorithm>#include<cmath>using namespace std;char s[1000005];long long dp[1000005];int main(){dp[0]=1;int i,d=0,k;long long ans=0;scanf("%d%s",&k,s);int l=strlen(s);for(i=0;i<l;++i){if(s[i]=='1') ++d;if(d>=k) ans+=dp[d-k];++dp[d];}cout<<ans<<endl;return 0;}