题目链接：http://codeforces.com/problemset/problem/327/A
这道题目有O(N^3)的做法，这里转化为动态规划求解，复杂度是O(N)
1 #include <cstdio> 2 #include <cstdlib> 3 #include <cstring> 4 #include <cmath> 5 #include <cctype> 6 #include <algorithm> 7 #include <queue> 8 #include <set> 9 #include <queue> 10 #include <list> 11 #include <map> 12 using namespace std; 13 #define INF 0x3f3f3f3f 14 int a[102], b[102], c[102]; 15 int main ( void ) 16 { 17 int n, n1=0, cnt=0; 18 while (~scanf("%d", &n)) 19 { 20 n1 = cnt = 0; 21 memset(a, 0, sizeof(a)); 22 memset(b, 0, sizeof(b)); 23 for (int i=1; i<=n; ++i){ 24 scanf("%d",a+i); if(a[i]) n1++; 25 if (a[i]) b[i]=-1; else b[i]=1; 26 } 27 c[0] = 0; 28 for (int i = 1; i <= n; ++i) 29 { 30 c[i] = c[i-1] + b[i]; 31 } 32 int Max = -INF, Min = c[0]; 33 for (int i = 1; i <= n; ++i) { 34 if (c[i] - Min > Max) Max = c[i]-Min; 35 if (c[i] < Min) Min = c[i]; 36 } 37 printf("%d\n",n1+Max); 38 } 39 return 0; 40 }
转化为子序列的最大连续和
