<四边形不等式优化>[NOI1995]石子合并

留个坑

挺套路的
明天来写个总结

#include<cstdio> 
#include<algorithm> 
inline int read() {
    int x = 0,f = 1;
    char c = getchar();
    while(c < '0' || c > '9') {if(c == '-') f = -1;c = getchar();}
    while(c <= '9' && c >= '0') x = x * 10 + c - '0',c = getchar();
    return x * f;
} 
const int maxn = 2007; 
int dp[maxn][maxn],s[maxn][maxn],cnt[maxn]; 
int sum[maxn]; 
int dpm[maxn][maxn];
int main () { 
    int n = read();
    for(int i = 1;i <= n;++ i) cnt[n + i] = cnt[i] = read(),sum[i] = sum[i - 1] + cnt[i]; 
    for(int i = n + 1;i <= n * 2;++ i) sum[i] = sum[i - 1] + cnt[i]; 
    for(int i = 1;i <= 2 * n;++ i) s[i][i] = i; 
    for(int i = n * 2 - 1;i >= 1;-- i) { 
        for(int j = i + 1;j <= n * 2;++ j) { 
            int tmp = 0x7fffffff,loc = 0; 
            dpm[i][j] = std::max(dpm[i][j - 1],dpm[i + 1][j]) + sum[j] - sum[i - 1]; 
            for(int k = s[i][j - 1];k <= s[i + 1][j];++ k) { 
                if(tmp >dp[i][k] + dp[k + 1][j] + sum[j] - sum[i - 1]) { 
                    tmp = dp[i][k] + dp[k + 1][j] + sum[j] - sum[i - 1]; 
                    loc = k; 
                } 
            } 
            dp[i][j] = tmp; 
            s[i][j] = loc; 
        } 
    } 
    int ansm = 0x7fffffff,ansx = 0;
    for(int i = 1;i <= n;++ i) {
        ansm = std::min(dp[i][i + n - 1],ansm) ; 
        ansx = std::max(dpm[i][i + n - 1],ansx) ; 
    }
    printf("%d\n%d",ansm,ansx);
    return 0;
}