题目描述
思路
RMQ 问题 ST算法
代码
#include <cstdio>
#include <cstring>
#define max(a, b) ((a) > (b) ? (a) : (b))
int n, m;
int arr[100005];
int f[100005][21], log[100005];
inline int read() {
int s = 0;
char ch = getchar();
while (ch < '0' || ch > '9') ch = getchar();
while (ch >= '0' && ch <= '9') s = s * 10 + ch - '0', ch = getchar();
return s;
}
int main() {
n = read(), m = read();
log[0] = -1;
for (int i = 1; i <= n; ++i) {
arr[i] = read();
log[i] = log[i >> 1] + 1;
f[i][0] = arr[i];
}
for (int i = 1; i <= 20; ++i) {
for (int j = 1; j + (1 << i) - 1 <= n; ++j) {
f[j][i] = max(f[j][i - 1], f[j + (1 << (i - 1))][i - 1]);
}
}
for (int i = 1, a, b, c; i <= m; ++i) {
a = read(), b = read();
c = log[b - a + 1];
printf("%d
", max(f[a][c], f[b - (1 << c) + 1][c]));
}
return 0;
}