分块函数学习 I hate it + 优化

#include <cstdio>#include <cmath>#include <algorithm>#include <iostream>#include <cstring>using namespace std;int a[200005],belong[200005],L[200005],R[200005],ans[200005];//  数据      所属的块     左界    右界    最大值数据/*  the first thing that I should do    1.将他们分组    2.区分左右值    3.算好他们的组中最大值*/int main(){    int m,n;    while (scanf("%d %d",&n,&m)!=EOF){        int len = sqrt(n);        int teams = n/len;        if (n%len != 0)teams ++;        for (int i = 0;i < 200005;i ++)            ans[i] = 0;        for (int i = 1;i <= n;i ++){            scanf("%d",&a[i]);            belong[i] = i/len;            if (i%len != 0)belong[i] ++;            ans[belong[i]] = max(ans[belong[i]],a[i]);        }        //  划分左右界        int j = 1;        for(int i=1;i<=teams;i++){            L[i]=R[i-1]+1;            R[i]=min(L[i]+len-1,n);        }//        L[j] = 1;//        for (int i = 1;i <= n-1;i ++){//            if(belong[i]!=belong[i+1]){//                R[j++] = i;//                L[j] = i+1;//            }//        }//        R[j] = n;        while (m --){            char str[2];            int x,y;            int maxscore;            scanf("%s %d %d",str,&x,&y);            if (str[0] == 'U'){                a[x] = y;                ans[belong[x]]=0;                //  所在的组为belong[x]                for (int i = L[belong[x]];i <= R[belong[x]];i ++){                    ans[belong[i]] = max(ans[belong[i]],a[i]);                }            }else {                maxscore=0;                if (belong[x] == belong[y]){                    for (int i = x;i <= y;i ++){                        maxscore = max(a[i],maxscore);                    }                }                else {                    for (int i = belong[x]+1;i <= belong[y]-1;i ++){                        maxscore = max(ans[i],maxscore);                    }                    for (int i = x;i <= R[belong[x]];i ++){                        maxscore = max(a[i],maxscore);                    }                    for (int i = L[belong[y]];i <= y;i ++)                        maxscore = max(a[i],maxscore);                }                printf("%d\n",maxscore);            }        }    }    return 0;}

分块优化

#include <iostream>#include <cmath>#include <algorithm>#include <memory.h>using namespace std;int R[200005],L[200005],hi[200005],team[200005],maxTeam[200005];int main(){    int m,n;    while (cin >> m >> n){        for (int i = 1;i <= m;i ++)            cin >> hi[i];        //开始分组        int len = sqrt(m);        int teams = (m+len-1)/len;        for (int i = 1;i <= m;i ++)            team[i] = (i + len - 1)/len;        //确定左右值        for (int i = 1;i <= teams;i ++){            L[i] = 1+len*(i-1);            R[i] = min(L[i]+len-1,m);        }        memset (maxTeam,0,sizeof(maxTeam));        for (int i = 1;i <= teams;i ++){            for (int j = L[i];j <= R[i];j ++)                maxTeam[i] = max(maxTeam[i],hi[j]);        }        while (n --){            int maxNum = 0;            char str[2];            cin >> str;            int Locate,Rocate;            cin >> Locate >> Rocate;            if (str[0] == 'Q'){                if (team[Locate] != team[Rocate]){                    for (int i = Locate;i <= R[team[Locate]];i ++)                        maxNum = max(maxNum,hi[i]);                    for (int i = team[Locate]+1;i <= team[Rocate]-1;i ++)                        maxNum = max(maxTeam[i],maxNum);                    for (int i = L[team[Rocate]];i <= Rocate;i ++)                        maxNum = max(maxNum,hi[i]);                }else {                    for (int i = Locate;i <= Rocate;i ++)                        maxNum = max(maxNum,hi[i]);                }                cout << maxNum << endl;            } else {                hi[Locate] = Rocate;                maxTeam[team[Locate]] = 0;                for (int i = L[team[Locate]];i <= R[team[Locate]];i ++)                    maxTeam[team[Locate]] = max(maxTeam[team[Locate]],hi[i]);            }        }    }    return 0;}

分块里面最最容易错的就是那个L[team[Locate]]那里面是组数啊，组数。非常容易错的