思路：dp[i][j][k]代表i-j区间加k个乘号的最大值，区间dp即可。 发现大数模板挺好用的，stringstream可以用于大数输入。
#include<bits/stdc++.h> using namespace std; const int maxn = 42; struct bign{ int d[maxn], len; void clean() { while(len > 1 && !d[len-1]) len--; } bign() { memset(d, 0, sizeof(d)); len = 1; } bign(int num) { *this = num; } bign(char* num) { *this = num; } bign operator = (const char* num){ memset(d, 0, sizeof(d)); len = strlen(num); for(int i = 0; i < len; i++) d[i] = num[len-1-i] - '0'; clean(); return *this; } bign operator = (int num){ char s[20]; sprintf(s, "%d", num); *this = s; return *this; } bign operator + (const bign& b){ bign c = *this; int i; for (i = 0; i < b.len; i++){ c.d[i] += b.d[i]; if (c.d[i] > 9) c.d[i]%=10, c.d[i+1]++; } while (c.d[i] > 9) c.d[i++]%=10, c.d[i]++; c.len = max(len, b.len); if (c.d[i] && c.len <= i) c.len = i+1; return c; } bign operator - (const bign& b){ bign c = *this; int i; for (i = 0; i < b.len; i++){ c.d[i] -= b.d[i]; if (c.d[i] < 0) c.d[i]+=10, c.d[i+1]--; } while (c.d[i] < 0) c.d[i++]+=10, c.d[i]--; c.clean(); return c; } bign operator * (const bign& b)const{ int i, j; bign c; c.len = len + b.len; for(j = 0; j < b.len; j++) for(i = 0; i < len; i++) c.d[i+j] += d[i] * b.d[j]; for(i = 0; i < c.len-1; i++) c.d[i+1] += c.d[i]/10, c.d[i] %= 10; c.clean(); return c; } bign operator / (const bign& b){ int i, j; bign c = *this, a = 0; for (i = len - 1; i >= 0; i--) { a = a*10 + d[i]; for (j = 0; j < 10; j++) if (a < b*(j+1)) break; c.d[i] = j; a = a - b*j; } c.clean(); return c; } bign operator % (const bign& b){ int i, j; bign a = 0; for (i = len - 1; i >= 0; i--) { a = a*10 + d[i]; for (j = 0; j < 10; j++) if (a < b*(j+1)) break; a = a - b*j; } return a; } bign operator += (const bign& b){ *this = *this + b; return *this; } bool operator <(const bign& b) const{ if(len != b.len) return len < b.len; for(int i = len-1; i >= 0; i--) if(d[i] != b.d[i]) return d[i] < b.d[i]; return false; } bool operator >(const bign& b) const{return b < *this;} bool operator<=(const bign& b) const{return !(b < *this);} bool operator>=(const bign& b) const{return !(*this < b);} bool operator!=(const bign& b) const{return b < *this || *this < b;} bool operator==(const bign& b) const{return !(b < *this) && !(b > *this);} string str() const{ char s[maxn]={}; for(int i = 0; i < len; i++) s[len-1-i] = d[i]+'0'; return s; } }dp[42][42][9]; istream& operator >> (istream& in, bign& x) { string s; in >> s; x = s.c_str(); return in; } ostream& operator << (ostream& out, const bign& x) { out << x.str(); return out; } int main() { int N,K; string str; cin>>N>>K; cin>>str; memset(dp,-1,sizeof(dp)); for(int len=1;len<=N;len++) { for(int i=0;i<=N-len;i++) { stringstream ss; bign v; ss<<str.substr(i,len);//输入 ss>>v; dp[i][i+len-1][0]=v; //cout<<v<<endl; } } for(int l=1;l<=K;l++) { for(int len=2;len<=N;len++) { for(int i=0;i<=N-len;i++) { int j=i+len-1; for(int sl=0;sl<l;sl++) { for(int kk=i+1;kk<=j;kk++) { dp[i][j][l]=max(dp[i][j][l],dp[i][kk-1][sl]*dp[kk][j][l-sl-1]); } } } } } cout<<dp[0][N-1][K]<<endl; }