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71 lines
1.8 KiB
71 lines
1.8 KiB
#include <bits/stdc++.h>
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using namespace std;
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const int N = 200010, M = 20;
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int w[N]; // 原始数组
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int f[N][M], g[N][M]; // 最大值结果数组，最小值结果数组
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int n, q;
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/*
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输入样例：
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6 3
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1 7 3 4 2 5
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1 5
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4 6
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2 2
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答案：
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6
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3
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0
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*/
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// 预处理最大值
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void rmqMax() {
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for (int j = 0; j < M; j++) // 注意是j在外层,类似于区间DP,长度在外层
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for (int i = 1; i + (1 << j) - 1 <= n; i++) // i(行)在内层
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if (j == 0) // base case 边界值
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f[i][j] = w[i];
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else
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f[i][j] = max(f[i][j - 1], f[i + (1 << j - 1)][j - 1]);
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}
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// 查询区间最大值
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int queryMax(int l, int r) {
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int len = r - l + 1;
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int k = log2(len);
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return max(f[l][k], f[r - (1 << k) + 1][k]);
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}
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// 预处理最小值
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void rmqMin() {
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for (int j = 0; j < M; j++) // 注意是j在外层,类似于区间DP,长度在外层
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for (int i = 1; i + (1 << j) - 1 <= n; i++) // i(行)在内层
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if (j == 0) // base case 边界值
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g[i][j] = w[i];
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else
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g[i][j] = min(g[i][j - 1], g[i + (1 << j - 1)][j - 1]);
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}
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// 查询区间最小值
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int queryMin(int l, int r) {
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int len = r - l + 1;
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int k = log2(len);
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return min(g[l][k], g[r - (1 << k) + 1][k]);
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}
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int main() {
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// 加快读入
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ios::sync_with_stdio(false), cin.tie(0);
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cin >> n >> q;
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for (int i = 1; i <= n; i++) cin >> w[i];
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rmqMax(); // ST表初始化
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rmqMin(); // ST表初始化
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while (q--) {
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int l, r;
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cin >> l >> r;
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printf("%d\n", queryMax(l, r) - queryMin(l, r));
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}
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return 0;
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} |