C. Another Problem on Strin
来源:互联网 发布:jquery ajax解析json 编辑:程序博客网 时间:2024/05/10 07:28
A string is binary, if it consists only of characters "0" and "1".
String v is a substring of string w if it has a non-zero length and can be read starting from some position in string w. For example, string "010" has six substrings: "0", "1", "0", "01", "10", "010". Two substrings are considered different if their positions of occurrence are different. So, if some string occurs multiple times, we should consider it the number of times it occurs.
You are given a binary string s. Your task is to find the number of its substrings, containing exactly k characters "1".
The first line contains the single integer k (0 ≤ k ≤ 106). The second line contains a non-empty binary string s. The length of s does not exceed 106 characters.
Print the single number — the number of substrings of the given string, containing exactly k characters "1".
Please do not use the %lld specifier to read or write 64-bit integers in С++. It is preferred to use the cin, cout streams or the %I64dspecifier.
11010
6
201010
4
10001010
0
In the first sample the sought substrings are: "1", "1", "10", "01", "10", "010".
In the second sample the sought substrings are: "101", "0101", "1010", "01010".
解题说明:此题要求统计包含k个1的字串的个数,可以用DP的方法来做,个数可以认为与0相关,在k个1之前有多少个0,那么个数就为多少,因为每次取子串可以少取一个0。首先统计1的个数,用num[cnt]表示第cnt个1前面0的个数,那么num[cnt-k]就表示满足条件的k个1之前0的个数,遍历时统计这个值即可。
#include <stdio.h>#include <stdlib.h>#define N 1000000int k, c, d, dp[N + 1] = {1}, i;long long ans;int main (void) {scanf ("%d\n", &k);while (c = getchar (), c != '\n') {if (c == '1') ++d;if (d >= k) ans += dp[d - k];++dp[d];}printf ("%I64d\n", ans);exit (EXIT_SUCCESS);}
- C. Another Problem on Strin
- CodeForces 165C - Another Problem on Strings
- codeforce 165C Another Problem on Strings
- CodeForces 165C - Another Problem on Strings
- codeforces-165C-Another Problem on Strings
- Another Problem on Strings
- Codeforces Round #112 (Div. 2) C Another Problem on Strings
- Codeforces Round #112 (Div. 2) C. Another Problem on Strings
- Codeforces Round #112 (Div. 2) C Another Problem on Strings
- Codeforces 165C Another Problem on Strings 【二分】
- codeforces 165C Another Problem on Strings 双指针
- CodeForces 165C Another Problem on Strings(公式推导)
- cf165c Another Problem on Strings
- Another Problem on Strings CodeForces
- codeforces 之 Another Problem on Strings
- Codeforces 165C Another Problem On Strings 尺取 Or 前缀和
- codeforces 165-C. Another Problem on Strings(计数+尺取)
- codeforces Another Problem on Strings 记录一个不慎
- 语音输入框
- LoadRunner无法连接 Load Generator。检查输出窗口,以获得详细信息
- 成为开发者的第一步 微信开发
- Linux如何实现开机启动程序详解
- jQuery使用技巧
- C. Another Problem on Strin
- 实现一个简单的服务端推送方案-实例篇Polling(服务端阻塞读,SLEEP方式读MYSQL)
- Sql Server 2008 收缩日志.
- CSS气泡效果
- 覆盖写文件用"r+"
- python 统计agent
- IIF函数
- 拓扑排序--关键路径实现
- MTK_HDMI 驱动