HDU1028 (整数拆分)
2015-10-23 12:00
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Ignatius and the Princess III
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 16191 Accepted Submission(s): 11407
"The second problem is, given an positive integer N, we define an equation like this:
N=a[1]+a[2]+a[3]+...+a[m];
a[i]>0,1<=m<=N;
My question is how many different equations you can find for a given N.
For example, assume N is 4, we can find:
4 = 4;
4 = 3 + 1;
4 = 2 + 2;
4 = 2 + 1 + 1;
4 = 1 + 1 + 1 + 1;
so the result is 5 when N is 4. Note that "4 = 3 + 1" and "4 = 1 + 3" is the same in this problem. Now, you do it!" Input The input contains several test cases. Each test case contains a positive integer N(1<=N<=120) which is mentioned above. The input is terminated by the end of file. Output For each test case, you have to output a line contains an integer P which indicate the different equations you have found. Sample Input 4 10 20 Sample Output 5 42 627 Author Ignatius.L 整数拆分问题 试着用数形结合的思想理解dfs 每个节点维护两个值,当前结点的值和剩下可传递给儿子的值,为了避免重复,所以每个节点的值都大于等于儿子节点的值
![](https://images2015.cnblogs.com/blog/826326/201510/826326-20151023115531130-1928323591.jpg)
/* ID: LinKArftc PROG: 1028.cpp LANG: C++ */ #include <map> #include <set> #include <cmath> #include <stack> #include <queue> #include <vector> #include <cstdio> #include <string> #include <utility> #include <cstdlib> #include <cstring> #include <iostream> #include <algorithm> using namespace std; #define eps 1e-8 #define randin srand((unsigned int)time(NULL)) #define input freopen("input.txt","r",stdin) #define debug(s) cout << "s = " << s << endl; #define outstars cout << "*************" << endl; const double PI = acos(-1.0); const double e = exp(1.0); const int inf = 0x3f3f3f3f; const int INF = 0x7fffffff; typedef long long ll; const int maxn = 150; int dp[maxn][maxn]; int dfs(int last, int res) { if (res <= 0) return 1; if (dp[last][res]) return dp[last][res]; int ret = 0; if (last >= res) { for (int i = res; i >= 1; i --) { ret += dfs(i, res - i); } } else { for (int i = last; i >= 1; i --) { ret += dfs(i, res - i); } } dp[last][res] = ret; return ret; } int main() { int n; while (~scanf("%d", &n)) { int ans = 0; memset(dp, 0, sizeof(dp)); for (int i = n; i >= 1; i --) ans += dfs(i, n - i); printf("%d\n", ans); } return 0; }
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