46 lines
1.4 KiB
C++
46 lines
1.4 KiB
C++
#include <cstdio>
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#include <cstring>
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#include <vector>
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#include <algorithm>
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using namespace std;
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typedef long long LL;
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const int maxn = 110;
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const LL mod = 1000000007;
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LL dp[maxn][maxn],c[maxn][maxn] = {1},f[maxn] = {1};
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void init() {
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for(int i = 1; i < maxn; ++i) {
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c[i][0] = c[i][i] = 1;
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f[i] = f[i-1]*i%mod;
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for(int j = 1; j < i; ++j)
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c[i][j] = (c[i-1][j-1] + c[i-1][j])%mod;
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}
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}
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char op[maxn];
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int main() {
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init();
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int n;
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while(~scanf("%d",&n)) {
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memset(dp,0,sizeof dp);
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for(int i = 0; i < n; ++i)
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scanf("%I64d",&dp[i][i]);
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scanf("%s",op);
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for(int i = 2; i <= n; ++i) {
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for(int j = 0; j + i <= n; ++j) {
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for(int k = j,t = j + i -1; k < t; ++k) {
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LL tmp;
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if(op[k] == '+')
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tmp = (f[t-k-1]*dp[j][k] + f[k-j]*dp[k+1][t])%mod;
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else if(op[k] == '-') {
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tmp = (f[t-k-1]*dp[j][k] - f[k-j]*dp[k+1][t])%mod;
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tmp = (tmp + mod)%mod;
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} else if(op[k] == '*') tmp = dp[j][k]*dp[k+1][t]%mod;
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tmp = tmp*c[t-j-1][k-j]%mod;
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dp[j][t] = (dp[j][t] + tmp + mod)%mod;
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}
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}
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}
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printf("%I64d\n",dp[0][n-1]);
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}
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return 0;
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}
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