RMQ算法之Sparse Table算法

目标算法：Sparse Table算法

应用范围：RMQ

#include<cstdio>#include<iostream>#include<algorithm>#include<cmath>using namespace std;const int maxn = 50005;int dpmax[maxn][20];int dpmin[maxn][20];int a[maxn];int n,m;void InitRmq(){    for(int i=0;i<n;i++)    {        dpmax[i][0] = a[i];        dpmin[i][0] = a[i];    }    for(int j=1;(1<<j)<=n;j++)    {        for(int i=0;i+(1<<j)-1<n;i++)        {            dpmax[i][j] = max(dpmax[i][j-1],dpmax[i+(1<<(j-1))][j-1]);            dpmin[i][j] = min(dpmin[i][j-1],dpmin[i+(1<<(j-1))][j-1]);        }    }}int getMax(int x,int y){    int k = (int)(log(y-x+1.0)/log(2.0));    return max(dpmax[x][k],dpmax[y-(1<<k)+1][k]);}int getMin(int x,int y){    int k = (int)(log(y-x+1.0)/log(2.0));    return min(dpmin[x][k],dpmin[y-(1<<k)+1][k]);}int main(){    while(~scanf("%d%d",&n,&m))    {        for(int i=0;i<n;i++)        {            scanf("%d",&a[i]);        }        InitRmq();        for(int i=0;i<m;i++)        {            int x,y;            scanf("%d%d",&x,&y);            printf("%d\n",getMax(x-1,y-1)-getMin(x-1,y-1));        }    }}