解题思路
代码
原始做法
#include <iostream>
#include <cstring>
using namespace std;
const int N = 1e5 + 10, K = 110;
int w[N], f[N][K][2];
int main() {
int n, k;
cin >> n >> k;
for (int i = 1; i <= n; i++) cin >> w[i];
memset(f, -0x3f, sizeof f);
for (int i = 0; i <= n; i++) f[i][0][0] = 0;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= k; j++) {
f[i][j][0] = max(f[i - 1][j][1] + w[i], f[i - 1][j][0]);
f[i][j][1] = max(f[i - 1][j][1], f[i - 1][j - 1][0] - w[i]);
}
}
int res = 0;
for (int i = 0; i <= k; i++) {
res = max(res, f[n][i][0]);
}
cout << res << endl;
return 0;
}
滚动数组优化
#include <iostream>
#include <cstring>
using namespace std;
const int N = 1e5 + 10, K = 110;
int w[N], f[K][2];
int main() {
int n, k;
cin >> n >> k;
for (int i = 1; i <= n; i++) cin >> w[i];
memset(f, -0x3f, sizeof f);
f[0][0] = 0;
for (int i = 1; i <= n; i++) {
for (int j = 1; j <= k; j++) {
f[j][0] = max(f[j][1] + w[i], f[j][0]);
f[j][1] = max(f[j][1], f[j - 1][0] - w[i]);
}
}
int res = 0;
for (int i = 0; i <= k; i++) {
res = max(res, f[i][0]);
}
cout << res << endl;
return 0;
}