poj 3276

来源：互联网发布：lua 编译linux 编辑：程序博客网时间：2024/06/06 20:37

尺选法、反转。

//212k, 344ms#include <iostream>#include <cstring>using namespace std;const int MAX_N = 5005;int n;int dir[MAX_N], f[MAX_N];int calc(int K) {    memset(f, 0, sizeof(f));    int res = 0, sum = 0;    for(int i=0; i+K<=n; i++) {        if((dir[i] + sum ) % 2 != 0) {            res++;            f[i] = 1;        }        sum += f[i];        if(i - K + 1 >= 0)            sum -= f[i-K+1];    }    for(int i=n-K+1; i<n; i++) {        if((dir[i] + sum) % 2 != 0)            return -1;        if(i-K+1 >= 0)            sum -= f[i-K+1];    }    return res;}void solve() {    int K = 1, M = n;    for(int k=1; k<=n; k++) {        int m = calc(k);        if(m >= 0 && M > m) {            M = m;            K = k;        }    }    printf("%d %d\n", K, M);}int main() {    freopen("in.txt", "r", stdin);    scanf("%d", &n);    getchar();    char c[2];    for(int i=0; i<n; i++) {        scanf("%s", c);        if(c[0] == 'B')            dir[i] = 1;        else if(c[0] == 'F')            dir[i] = 0;    }    solve();    fclose(stdin);    return 0;}

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