HDOJ 5672 String

String

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)

Total Submission(s): 965    Accepted Submission(s): 313

Problem Description

There is a string S.S only contain lower case English character.(10≤length(S)≤1,000,000)
How many substrings there are that contain at least k(1≤k≤26) distinct characters?

 

Input

There are multiple test cases. The first line of input contains an integerT(1≤T≤10) indicating the number of test cases. For each test case:

The first line contains string S.
The second line contains a integer k(1≤k≤26).

 

Output

For each test case, output the number of substrings that contain at leastk dictinct characters.

 

Sample Input

2abcabcabca4abcabcabcabc3

 

Sample Output

055

 

中文题面： BC Round #81 (div.2)1003  

题解：额，组合数学和模拟被学弟吊打(；′⌒`)  /(ㄒoㄒ)/~~  想多了，还以为这一题要DP计数，感觉不会搞。 学弟直接模拟计数。我这组合数学太渣渣。。。 

 

按顺序遍历字符串，记录出现的不同字母的个数cnt，和每种字母出现的数量。 当cnt==k时，以当前字符串为子串的子串共有len-i个。然后将最左边的减去，依次记录下去。

代码如下：

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;char s[1000010];int num[30];int main(){int k,t;scanf("%d",&t);while(t--){scanf("%s%d",s,&k);int len=strlen(s);int cnt=0,left=0;long long ans=0;memset(num,0,sizeof(num));for(int i=0;i<len;++i){int temp=s[i]-'a';if(num[temp])num[temp]++;else{num[temp]++;cnt++;}if(cnt==k){ans+=(len-i);while(1){temp=s[left]-'a';num[temp]--;left++;if(!num[temp]){cnt--;break;}elseans+=(len-i);}}}printf("%I64d\n",ans);}return 0;}