POJ - 3276 开关问题

反转问题，要注意每次rev操作是严格等于k的，否则非法

#include
#include
#include
#include
#define rep(i,j,k) for(int i=j;i<=k;i++)
using namespace std;
const int maxn = 5e3+11;
typedef pair P;
bool rev[maxn];//rev[i]:[i..i+k-1]
bool dir[maxn];
char str[6];
int n,sum[maxn];
int check(int i,int k){
    if(k>=2){
        if(i+1-k>0) return sum[i-1]-sum[i-k];
        else  return sum[i-1];
    }else{
        return 0;
    }
}
int main(){
    while(scanf("%d",&n)^-1){
        rep(i,0,n-1) {scanf("%s",str); dir[i+1]=(str[0]=='F');}
        int cnt=0;
        rep(i,1,n) cnt+=dir[i];
        P best(n-cnt,1);//k==1
        rep(k,2,n){
            int m=0;
            memset(rev,0,sizeof rev);
            memset(sum,0,sizeof sum);
            rep(i,1,n-k+1){
                if((check(i,k)+dir[i]) &1){
                    sum[i]=sum[i-1];
                }
                else{
                    m++;
                    rev[i]=1;
                    sum[i]=sum[i-1]+rev[i];
                }
            }
            rep(i,n-k+2,n){
                if((check(i,k)+dir[i]) &1){sum[i]=sum[i-1];}
                else{m=0x3f3f3f3f;break;}
            }
            if(m

转载于:https://www.cnblogs.com/caturra/p/8297412.html