hdu 3308 LCIS(线段树)

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题目链接：hdu 3308 LCIS

题目大意：给定一个序列，两种操作：

Q l r：查询区间l，r中的最长连续递增序列长度
U p x：将位置p上的数改成x

解题思路：线段树上的区间合并，这是在左右子树合并的时候要判断一下是否满足递增即可。

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 1e5 + 5;int N, M, a[maxn];#define lson(x) ((x)<<1)#define rson(x) (((x)<<1)|1)int lc[maxn << 2], rc[maxn << 2];int L[maxn << 2], R[maxn << 2], S[maxn << 2];void pushup (int u) {    int mid = (lc[u] + rc[u]) / 2;    S[u] = max(max(S[lson(u)], S[rson(u)]), (a[mid] < a[mid+1] ? R[lson(u)] + L[rson(u)] : 0));    L[u] = L[lson(u)] + (L[lson(u)] == rc[lson(u)] - lc[lson(u)] + 1 && a[mid] < a[mid + 1] ? L[rson(u)] : 0);    R[u] = R[rson(u)] + (R[rson(u)] == rc[rson(u)] - lc[rson(u)] + 1 && a[mid] < a[mid + 1] ? R[lson(u)] : 0);}void build (int u, int l, int r) {    lc[u] = l;    rc[u] = r;    if (l == r) {        L[u] = R[u] = S[u] = 1;        return;    }    int mid = (l + r) / 2;    build(lson(u), l, mid);    build(rson(u), mid + 1, r);    pushup(u);}void modify (int u, int x, int v) {    if (lc[u] == x && rc[u] == x) {        a[x] = v;        return;    }    int mid = (lc[u] + rc[u]) / 2;    if (x <= mid)        modify(lson(u), x, v);    else        modify(rson(u), x, v);    pushup(u);}int query (int u, int l, int r) {    if (l <= lc[u] && rc[u] <= r)        return S[u];    int mid =(lc[u] + rc[u]) / 2, ret;    if (r <= mid)        ret = query(lson(u), l, r);    else if (l > mid)        ret = query(rson(u), l, r);    else {        int ll = query(lson(u), l, r);        int rr = query(rson(u), l, r);        int A = min(R[lson(u)], mid - l + 1);        int B = min(L[rson(u)], r - mid);        ret = max(max(ll, rr), a[mid] < a[mid + 1] ? A + B : 0);    }    return ret;}int main () {    int cas;    scanf("%d", &cas);    while (cas--) {        scanf("%d%d", &N, &M);        for (int i = 0; i < N; i++)            scanf("%d", &a[i]);        build(1, 0, N-1);        int l, r;        char op[5];        while (M--) {            scanf("%s%d%d", op, &l, &r);            if (op[0] == 'U')                modify(1, l, r);            else                printf("%d\n", query(1, l, r));        }    }    return 0;}

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