Think:
1知识点:数位DP+二进制
2题意:输入一个区间判断有多少个“Round Number”,“Round Number”的定义为其二进制表示中0的数量大于等于1的数量
以下为Accepted代码
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
int dp[40][40][40], tp, link[40];
int dfs(int pos, int cnt0, int cnt1, bool lead, bool is_max);
int solve(int x);
int main(){
memset(dp, -1, sizeof(dp));
int l, r;
while(~scanf("%d %d", &l, &r)){
printf("%d\n", solve(r)-solve(l-1));
}
return 0;
}
int solve(int x){
tp = 0;
while(x){
link[tp++] = x%2;
x >>= 1;
}
return dfs(tp-1, 0, 0, true, true);
}
int dfs(int pos, int cnt0, int cnt1, bool lead, bool is_max){
if(pos == -1)
return cnt0 >= cnt1 && !lead;
if(!is_max && !lead && ~dp[pos][cnt0][cnt1])
return dp[pos][cnt0][cnt1];
int up_top = 1;
if(is_max)
up_top = link[pos];
int sum = 0;
for(int i = 0; i <= up_top; i++){
if(lead){
if(i == 0){
sum += dfs(pos-1, 0, 0, true, false);
}
else if(i == 1){
sum += dfs(pos-1, 0, 1, false, is_max && i == up_top);
}
}
else {
if(i == 0){
sum += dfs(pos-1, cnt0+1, cnt1, false, is_max && i == up_top);
}
else if(i == 1){
sum += dfs(pos-1, cnt0, cnt1+1, false, is_max && i == up_top);
}
}
}
if(!is_max)
dp[pos][cnt0][cnt1] = sum;
return sum;
}