Codeforces 165C Another Problem on Strings two minutes

Topic Link: codeforces 165C Another Problem on Strings

C. Another Problem on Strings
Time limit per test2 seconds
Memory limit per test256 megabytes
Inputstandard input
Outputstandard output
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 are read starting from some position in string W. F or example, string "010" has six substrings: "0", "1", "0", "01", "10", "010". Two substrings are considered different if their positions of occurrence are. So, if some string occurs multiple times, we should consider it the number of it occurs.

You are given a binary string s. Your task is to find the number of it substrings, containing exactly k characters "1".

Input
The "The" the 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 characters.

Output
Print the single number-the number of substrings of the given string, containing exactly k characters "1".

Please don't use the%lld specifier to read or write 64-bit integers inс++. It is preferred to use the CIN, cout streams or the%i64d specifier.

Examples
Input
1
1010
Output
6
Input
2
01010
Output
4
Input
100
01010
Output
0
Note
In the the sought substrings are: "1", "1", "10", "01", "10", "010".

In the second sample the sought substrings are: "101", "0101", "1010", "01010".

Q: Ask you to have a strict number of K 1 substring.

Idea: preprocessing prefixes and, then two points.

AC Code:

#include <iostream> #include <cstdio> #include <cmath> #include <algorithm> #include < cstring> #include <queue> #define CLR (A, B) memset (A, (b), sizeof (a)) #define FI #define SE second using NA
Mespace std;
typedef long Long LL;
typedef pair<int, int> PII;
const int MAXN = 1e6 +10;
const int INF = 0X3F3F3F3F;
const int MOD = 1e9 + 7;
void Add (ll &x, ll y) {x + y; x%= MOD;} char STR[MAXN];
int SUM[MAXN];
    int find (int l, int r, int p, int v) {int ans = R + 1;
        while (R >= l) {int mid = (L + r) >> 1;
            if (Sum[mid]-sum[p-1] >= v) {ans = mid;
        R = mid-1;
        else {L = mid + 1;
} return ans;
    int main () {int k;
        while (scanf ("%d", &k)!= EOF) {scanf ("%s", str+1); int len = strlen (str+1);
        Sum[0] = 0;
        for (int i = 1; I <= len i++) {Sum[i] = Sum[i-1] + (str[i] = = ' 1 ');
    }    LL ans = 0;
            for (int i = 1; I <= len i++) {int s = find (i, Len, I, K);
            if (s = = len + 1) continue;
            int t = find (i, Len, I, k+1);
        Ans = t-s;
    printf ("%lld\n", ans);
return 0; }