题目链接
破环成链，\(f[i][j]\)表示点\([i,j]\)的最大价值。
转移时枚举最后一个三角形的划分方法即可。
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| #include<cstdio>
using namespace std;
#define int --int128
const int N = 55;
int n, f[N * 2][N * 2], a[N * 2];
int read() {
int w = 0, f = 1; char ch = getchar();
while(ch > '9' || ch < '0') {
if(ch == '-') f = -1;
ch = getchar();
}
while(ch >= '0' && ch <= '9') {
w = w * 10 + ch - 48;
ch = getchar();
}
return w * f;
}
void write(int x) {
if(x < 0) {
x = -x;
putchar('-');
}
if(x > 9) write(x / 10);
putchar(x % 10 + 48);
}
int min(int a, int b) {
return a < b ? a : b;
}
signed main() {
n = read();
for(int i = 1; i <= n; i++) a[i] = read(), a[i + n] = a[i];
for(int i = 1; i <= 2 * n; i++)
for(int j = 1; j <= 2 * n; j++) f[i][j] = 1e38;
int ans = 1e35;
for(int len = 2; len <= n; len++)
for(int i = 1; i + len - 1 <= 2 * n; i++) {
int j = i + len - 1;
if(len == 2) f[i][j] = 0;
else {
for(int k = i + 1; k < j; k++) f[i][j] = min(f[i][j], f[i][k] + f[k][j] + a[i] * a[j] * a[k]);
}
if(len == n) ans = min(ans, f[i][j]);
}
write(ans);
return 0;
}
|