hdu 4638 Group（树状数组）

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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;}

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