SWUN OJ 1749(DP + 线段树)

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SWUN 1749

题目链接

思路：lis一样的状态转移方程，不过要利用线段树去维护，每次更新到i，相应的维护i - d之后的区间的最大值，不断转移即可

代码：

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;#define lson(x) ((x<<1)+1)#define rson(x) ((x<<1)+2)const int N = 100005;int n, d, A[N];struct Node {    int l, r, v;} node[N * 4];void pushup(int x) {    node[x].v = max(node[lson(x)].v, node[rson(x)].v);}void build(int l, int r, int x = 0) {    int mid = (l + r) / 2;    node[x].l = l; node[x].r = r; node[x].v = 0;    if (l == r) {return;    }    build(l, mid, lson(x));    build(mid + 1, r, rson(x));    pushup(x);}void add(int v, int val, int x = 0) {    if (node[x].l == node[x].r) {node[x].v = max(node[x].v, val);return;    }    int mid = (node[x].l + node[x].r) / 2;    if (v <= mid) add(v, val, lson(x));    else add(v, val, rson(x));    pushup(x);}int query(int l, int r, int x = 0) {    if (r < l) return 0;    if (node[x].l >= l && node[x].r <= r)return node[x].v;    int mid = (node[x].l + node[x].r) / 2;    int ans = 0;    if (l <= mid) ans = max(ans, query(l, r, lson(x)));    if (r > mid) ans = max(ans, query(l, r, rson(x)));    return ans;}int dp[N];int main() {    while (~scanf("%d%d", &n, &d)) {build(0, 100000);int ans = 0;for (int i = 1; i <= d; i++) {    scanf("%d", &A[i]);    dp[i] = 1;}for (int i = d + 1; i <= n; i++) {    scanf("%d", &A[i]);    add(A[i - d - 1], dp[i - d - 1]);    dp[i] = query(1, A[i] - 1) + 1;    ans = max(dp[i], ans);}printf("%d\n", ans);    }    return 0;}

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