hdu 4638 Group（树状数组）

题目链接：hdu 4638 Group

代码

#include <cstdio>
#include <cstring>
#include <vector>
#include <algorithm>

using namespace std;
#define lowbit(x) ((x)&(-x))
const int maxn = 100005;
typedef pair<int,int> pii;

int N, fenw[maxn];

void add(int x, int v) {
    while (x <= N) {
        fenw[x] += v;
        x += lowbit(x);
    }
}

int sum(int x) {
    int ret = 0;
    while (x) {
        ret += fenw[x];
        x -= lowbit(x);
    }
    return ret;
}

int M, A[maxn], P[maxn], ans[maxn];
vector<pii> G[maxn];

void init () {
    scanf("%d%d", &N, &M);
    for (int i = 1; i <= N; i++) {
        scanf("%d", &A[i]);
        G[i].clear();
    }

    memset(P, -1, sizeof(P));
    memset(fenw, 0, sizeof(fenw));

    int l, r;
    for (int i = 1; i <= M; i++) {
        scanf("%d%d", &l, &r);
        G[l].push_back(make_pair(r, i));
    }
}

void solve () {
    for (int i = N; i; i--) {
        add(i, 1);
        P[A[i]] = i;
        int pre = P[A[i]-1], suf = P[A[i]+1];
        if (pre != -1) add(pre, -1);
        if (suf != -1) add(suf, -1);

        for (int j = 0; j < G[i].size(); j++) {
            int r = G[i][j].first;
            int k = G[i][j].second;
            ans[k] = sum(r) - sum(i-1);
        }
    }
}

int main () {
    int cas;
    scanf("%d", &cas);
    while (cas--) {
        init();
        solve();
        for (int i = 1; i <= M; i++)
            printf("%d\n", ans[i]);
    }
    return 0;
}