pku 2181 牛儿上天

#include <iostream>using namespace std;#define MAX 150001int A[MAX];int main(){int n;int M[MAX], N[MAX];scanf("%d", &n);for(int i = 1; i <= n; ++i)scanf("%d", &A[i]);//dp// M[i]: 前i个元素中有奇数个元素的最大值// N[i]: 前i个元素中有偶数个元素的最大值//维护前i, i+1,...个元素中奇数个的最大值,与偶数个的最大值M[1] = 0, N[1] = A[1];for(int i = 1; i <= n-1; ++i){M[i+1] = max(M[i], N[i]-A[i+1]);N[i+1] = max(N[i], M[i]+A[i+1]);}printf("%d/n", max(M[n], N[n]));return 0;}//上程序的节省空间版本:#include <iostream>using namespace std;#define MAX 150001int A[MAX];int main(){int n;int M, N;scanf("%d", &n);for(int i = 1; i <= n; ++i)scanf("%d", &A[i]);//dp// M[i]: L[i]中有奇数个元素的最大值// N[i]: L[i]中有偶数个元素的最大值M = 0, N = A[1];for(int i = 1; i <= n-1; ++i){int MTmp = M;M = max(M, N-A[i+1]);N = max(N, MTmp+A[i+1]);}printf("%d/n", max(M, N));return 0;}