【HDOJ】1258 Sum It Up

典型的深搜，剪枝的时候需要跳过曾经搜索过的相同的数目，既满足nums[i]=nums[i-1]&&visit[i-1]==0，visit[i-1]==0可以说明该点已经测试过。

 1 #include <stdio.h>
 2 #include <string.h>
 3 
 4 #define MAXNUM 1005
 5 
 6 int nums[MAXNUM];
 7 int visit[MAXNUM];
 8 int t, n;
 9 
10 void output() {
11     int i, j=0;
12 
13     for (i=0; i<t; ++i) {
14         if (j && visit[i])
15             printf("+%d", nums[i]);
16         if (j==0 && visit[i]) {
17             printf("%d", nums[i]);
18             j = 1;
19         }
20     }
21     printf("
");
22 }
23 
24 int check(int index, int sum) {
25     if (index<0 || index>=t || visit[index] || sum+nums[index]>n)
26         return 0;
27     return 1;
28 }
29 
30 int dfs(int beg, int sum) {
31     int i, val=0;
32 
33     if (sum == n) {
34         output();
35         return 1;
36     }
37 
38     for (i=beg; i<t; ++i) {
39         if (i>beg && nums[i]==nums[i-1] && visit[i-1]==0)
40             continue;
41         if (check(i, sum)) {
42             visit[i] = 1;
43             if (dfs(i+1, sum+nums[i]))
44                 val = 1;
45             visit[i] = 0;
46         }
47     }
48 
49     return val;
50 }
51 
52 int main() {
53     int i;
54 
55     while (scanf("%d%d", &n, &t)!=EOF && (n||t)) {
56         for (i=0; i<t; ++i)
57             scanf("%d", &nums[i]);
58         memset(visit, 0, sizeof(visit));
59         printf("Sums of %d:
", n);
60         if ( !dfs(0, 0) )
61             printf("NONE
");
62     }
63     return 0;
64 }