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refactor(P4342.cpp): 优化动态规划实现并修复计算逻辑

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重构动态规划的实现方式，将原来的双重循环改为基于长度的遍历，提高代码可读性和效率。同时修复了最大值和最小值的计算逻辑，确保正确处理加法和乘法操作。添加结果收集和输出部分，完善程序功能。
This commit is contained in:
Zengtudor 2025-08-29 10:14:01 +08:00
parent 84eee83148
commit 22e2db73d9
1 changed files with 56 additions and 11 deletions
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67
src/8/28/P4342.cpp
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@ -24,6 +24,7 @@ dpmin[i][j] = 1e9
dp[i][i]=arr[i]
*/
#include <algorithm>
#include <cstdint>
#include <iostream>
#include <istream>
@ -51,17 +52,61 @@ int main(){
op[i+n]=op[i];
}
std::vector<std::vector<ll>> dpmax,dpmin;
for(ll s=1;s<n;s++){
ll e = s+n-1;
dpmax.clear();
dpmax.resize(n21,std::vector<ll>(n21,-1e9));
dpmin.clear();
dpmin.resize(n21,std::vector<ll>(n21,1e9));
for(ll i=s;i<=e;i++){
dpmax[i][i]=op[i][1];
}
for(ll i=s;i<=e;i++){
dpmax.clear();
dpmax.resize(n21,std::vector<ll>(n21,-1e9));
dpmin.clear();
dpmin.resize(n21,std::vector<ll>(n21,1e9));
for(ll i=1;i<=2*n;i++){
dpmax[i][i]=op[i][1];
dpmin[i][i]=op[i][1];
}
for(ll len=2;len<=n;len++){
for(ll i=1;i<=2*n-len;i++){
ll j=i+len-1;
for(ll k=i;k<j;k++){
if(op[k+1][0]==add){ //注意是k+1
dpmax[i][j]=std::max(
dpmax[i][k]+dpmax[k+1][j],
dpmax[i][j]
);
dpmin[i][j]=std::min(
dpmin[i][k]+dpmin[k+1][j],
dpmin[i][j]
);
}else{
dpmax[i][j]=std::max({
dpmax[i][j],
dpmax[i][k]*dpmax[k+1][j],
dpmin[i][k]*dpmin[k+1][j],
dpmax[i][k]*dpmin[k+1][j],
dpmin[i][k]*dpmax[k+1][j]
});
dpmin[i][j]=std::min({
dpmin[i][j],
dpmax[i][k]*dpmax[k+1][j],
dpmin[i][k]*dpmin[k+1][j],
dpmax[i][k]*dpmin[k+1][j],
dpmin[i][k]*dpmax[k+1][j]
});
}
}
}
}
ll ans=-1e9;
std::vector<ll> edgs;
for(ll i=1;i<=n;i++){
ll nans=dpmax[i][i+n-1];
if(nans>ans){
ans=nans;
edgs.clear();
edgs.push_back(i);
}else if(nans==ans){
edgs.push_back(i);
}
}
std::cout<<ans<<"\n";
for(ll i:edgs){
std::cout<<i<<" ";
}
std::cout<<"\n";
}