POJ 3264 Balanced Lineup(ST表)

// POJ 3264 Balanced Lineup.cpp 运行/限制：3375ms/5000ms
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
using namespace std;
int n;
int a[50005], minValue[50005][20], maxValue[50005][20], upper[50005];//upper[i]相当于(int)floor(log(i)/log(2.0))
void init() {
upper[0] = -1;
for (int i = 1; i <= 50005; i++) {
upper[i] = ((i & (i - 1)) == 0) ? upper[i - 1] + 1 : upper[i - 1];
}
}
void rmq_init() {//离线预处理
for (int i = 1; i <= n; i++) {
scanf("%d", &a[i]);
minValue[i][0] = maxValue[i][0] = a[i];
}
int k = upper
;
for (int i = 1; i <= k; i++) {
for (int j = 1; j + (1 << i) - 1 <= n; j++) {
minValue[j][i] = min(minValue[j][i - 1], minValue[j + (1 << (i - 1))][i - 1]);
maxValue[j][i] = max(maxValue[j][i - 1], maxValue[j + (1 << (i - 1))][i - 1]);
}
}
}
int rmq(int le, int rig) {//在线查询
int k = upper[rig - le + 1];
return max(maxValue[le][k], maxValue[rig - (1 << k) + 1][k]) - min(minValue[le][k], minValue[rig - (1 << k) + 1][k]);
}
int main() {
int a, b, q;
init();
while (scanf("%d%d", &n, &q) != EOF) {
rmq_init();
for (int i = 0; i < q; i++) {
scanf("%d%d", &a, &b);
printf("%d\n", rmq(a, b));
}
}
return 0;
}