大意:给定后缀表达式, 每次操作可以添加一个字符, 可以交换两个字符的位置, 相邻数字可以看做一个整体也可以分开看, 求合法所需最少操作数.
数字个数一定为星号个数+1, 添加星号一定不会更优.
先判断若星号过多, 直接在最左边添上数字, 遍历过程中若星号还多的话把星号与右侧数字交换.
#include <iostream> #include <algorithm> #include <cstdio> #include <math.h> #include <set> #include <map> #include <queue> #include <string> #include <string.h> #include <bitset> #define REP(i,a,n) for(int i=a;i<=n;++i) #define PER(i,a,n) for(int i=n;i>=a;--i) #define hr putchar(10) #define pb push_back #define lc (o<<1) #define rc (lc|1) #define mid ((l+r)>>1) #define ls lc,l,mid #define rs rc,mid+1,r #define x first #define y second #define io std::ios::sync_with_stdio(false) #define endl ' ' #define DB(a) ({REP(__i,1,n) cout<<a[__i]<<' ';hr;}) using namespace std; typedef long long ll; typedef pair<int,int> pii; const int P = 1e9+7, INF = 0x3f3f3f3f; ll gcd(ll a,ll b) {return b?gcd(b,a%b):a;} ll qpow(ll a,ll n) {ll r=1%P;for (a%=P;n;a=a*a%P,n>>=1)if(n&1)r=r*a%P;return r;} ll inv(ll x){return x<=1?1:inv(P%x)*(P-P/x)%P;} inline int rd() {int x=0;char p=getchar();while(p<'0'||p>'9')p=getchar();while(p>='0'&&p<='9')x=x*10+p-'0',p=getchar();return x;} //head #ifdef ONLINE_JUDGE const int N = 1e6+10; #else const int N = 111; #endif int n; char s[N]; void work() { scanf("%s", s+1); n = strlen(s+1); int star = 0, num = 0; REP(i,1,n) { if (s[i]=='*') ++star; else ++num; } int left_num = 0, ans = 0; if (num<=star) { left_num += star-num+1; ans += left_num; } int now = n; REP(i,1,n) { while (i<now&&s[now]=='*') --now; if (s[i]=='*') { if (--left_num<1) { ++ans,--now; left_num+=2; } } else ++left_num; } printf("%d ", ans); } int main() { int t; scanf("%d", &t); while (t--) work(); }