nyoj--119 士兵杀敌（三）(RMQ)

题解

#include <iostream>
#include <cstdio>
#include <cmath>
#include <algorithm>
using namespace std;

const int maxn = 100000 + 10;
int   maxnum[maxn][17], minnum[maxn][17]; //2^17 = 131072
int   n, q;

void initRMQ()
{
int a;
for(int i = 1; i <= n; ++i){
scanf("%d", &a);
maxnum[i][0] = minnum[i][0] = a;
}
int k = int(log(n) / log(2));
for(int j = 1; j <= k; ++j)
{
for(int i = 1; i <= n; ++i)
{
if(i + (1 << j) - 1 <= n)
{
maxnum[i][j] = max(maxnum[i][j - 1], maxnum[i + (1 << (j - 1))][j - 1]);
minnum[i][j] = min(minnum[i][j - 1], minnum[i + (1 << (j - 1))][j - 1]);
}
}
}
}

inline int queryRMQ(int flag, int a, int b)
{
int k = int(log(b - a + 1) / log(2.0));
return flag ? max(maxnum[a][k], maxnum[b - (1 << k) + 1][k]) : min(minnum[a][k], minnum[b - (1 << k) + 1][k]);
}

int main()
{
cin >> n >> q;
initRMQ();
while(q--)
{
int a, b;
scanf("%d %d", &a, &b);
printf("%d\n", queryRMQ(1, a, b) - queryRMQ(0, a, b));
}
return 0;
}