53 lines
1.3 KiB
C++
53 lines
1.3 KiB
C++
#include <algorithm>
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#include <cstdio>
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#include <cstring>
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const int INF = 0x3f3f3f3f;
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using namespace std;
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const int N = 50010;
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int a[N];
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int n, q;
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// 树状数组模板
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int c1[N], c2[N]; // c1:维护最大值，c2：维护最小值
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int lowbit(int x) {
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return x & -x;
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}
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void update(int x, int d) {
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for (int i = x; i < N; i += lowbit(i)) c1[i] = max(c1[i], d), c2[i] = min(c2[i], d);
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}
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int query(int x, int y) {
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int mx = 0, mi = INF;
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while (y >= x) { // 右侧到左侧
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mx = max(mx, a[y]), mi = min(mi, a[y]); // 每次最后侧的点参加评比
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for (--y; y - x >= lowbit(y); y -= lowbit(y)) // 从x~y-1检查每个片断
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mx = max(mx, c1[y]), mi = min(mi, c2[y]);
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}
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return mx - mi;
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}
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int main() {
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#ifndef ONLINE_JUDGE
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freopen("POJ3264.in", "r", stdin);
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#endif
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memset(c1, 0, sizeof c1);
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memset(c2, 0x3f, sizeof c2); // 最小值，需要先设置最大，最大值默认的就是0，不需要设置
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scanf("%d %d", &n, &q);
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for (int i = 1; i <= n; i++) {
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scanf("%d", &a[i]);
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update(i, a[i]);
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}
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while (q--) {
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int a, b;
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scanf("%d %d", &a, &b);
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printf("%d\n", query(a, b));
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}
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return 0;
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} |