hdu 5568（dp+大数模拟）

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题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=5568

官方题解：

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 105;struct Bign {    int n, s[maxn<<1];    Bign (int t = 0) { init(); s[0] = t; }    void init () { n = 1; memset(s, 0, sizeof(s)); }    void add(const Bign& a) {        int res = 0;        for (int i = 0; i < a.n || i < n; i++) {            if (i < a.n) res += a.s[i];            if (i < n) res += s[i];            s[i] = res % 10;            res /= 10;        }        n = max(a.n, n);        while (res) {            s[n++] = res % 10;            res /= 10;        }    }}dp[maxn][maxn], ONE(1);int N, K, A[maxn];void solve () {    Bign ans(0);    for (int i = 1; i <= N; i++) {        for (int j = 1; j <= K; j++)            dp[i][j].init();    }    for (int i = 1; i <= N; i++) {        dp[i][1].add(ONE);        ans.add(dp[i][K]);        for (int j = i + 1; j <= N; j++) if (A[i] < A[j]) {            for (int k = 2; k <= K; k++) dp[j][k].add(dp[i][k-1]);        }    }    for (int i = ans.n-1; i >= 0; i--) printf("%d", ans.s[i]);    printf("\n");}int main() {    while (scanf("%d%d", &N, &K) == 2) {        for (int i = 1; i <= N; i++) scanf("%d", &A[i]);        solve();    }    return 0;}

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