题解 | 小红的华撃串

//使用暴力枚举求解  把四段调整为「1-0-1-0」或「0-1-0-1」
#include <stdio.h>
#include <string.h>
int min(int a,int b)
{
    return a<b?a:b;
}
int main() 
{
    int n;
    char s[501];
    scanf("%d %s", &n, s);
    int pre_0[501]={0},pre_1[501]={0};
    for(int i=1;i<=n;i++)
    {
        pre_0[i]=pre_0[i-1]+(s[i-1]=='0'?1:0);
        pre_1[i]=pre_1[i-1]+(s[i-1]=='1'?1:0);
    }
    int ans=n;
    for(int i=1;i<=n;i++)
    {
        for(int j=i+1;j<=n;j++)
        {
            for(int k=j+1;k<=n;k++)
            {
                int cnt1=0;
                cnt1+=pre_1[i]-pre_1[0];
                cnt1+=pre_0[j]-pre_0[i];
                cnt1+=pre_1[k]-pre_1[j];
                cnt1+=pre_0[n]-pre_0[k];
                int cnt2=0;
                cnt2+=pre_0[i]-pre_0[0];
                cnt2+=pre_1[j]-pre_1[i];
                cnt2+=pre_0[k]-pre_0[j];
                cnt2+=pre_1[n]-pre_1[k];
                ans=min(ans,min(cnt1,cnt2));
            }
        }
    }
    printf("%d",ans);
    return 0;
}