买不到的数目

从小到大递推动归，初始值a,b能组成，然后递推出所有组合。

#include<stdio.h>#include<algorithm>#include<queue>#include<string.h>#include<ctype.h>#include<set>#include<math.h>using namespace std;#define MAXN  1000005bool dp[MAXN];int main(){int a, b;memset(dp, 0, sizeof(dp));scanf("%d%d", &a, &b);dp[a] = dp[b] = true;for (int num = max(a, b) + 1; num < MAXN; num++){if (dp[num - a] == true || dp[num - b] == true){dp[num] = true;}}for (int i = MAXN - 1; i >= 1; i--){if (dp[i] == false){printf("%d\n", i);break;}}return 0;}