这是我今天遇到最奇怪的问题，希望有人帮我解释一下。。。
一开始我能得90分：
#include<iostream> #include<cstdio> #include<cmath> #include<ctime> #include<queue> #include<algorithm> #include<stack> #include<cstring> using namespace std; #define duke(i,a,n) for(int i = a;i <= n;i++) #define lv(i,a,n) for(int i = a;i >= n;i--) #define clean(a) memset(a,0,sizeof(a)) typedef long long ll; const int INF = 1 << 30; const ll mod = 12345678910; typedef double db; template <class T> void read(T &x) { char c; bool op = 0; while(c = getchar(), c < '0' || c > '9') if(c == '-') op = 1; x = c - '0'; while(c = getchar(), c >= '0' && c <= '9') x = x * 10 + c - '0'; if(op) x = -x; } template <class T> void write(T x) { if(x < 0) putchar('-'), x = -x; if(x >= 10) write(x / 10); putchar('0' + x % 10); } ll n,s = 0; ll p[50000],x,ans = 0; ll num = 0; int main() { read(n); duke(i,1,n) { read(x); if(x == 0) { p[++num] = x; } else { s = 0; while (p[num] != 0) { s += p[num]; s = s % mod; num--; } if(s == 0) { p[num] = 1; } else { p[num] = s * 2 % mod; } } } ll tot = 0; duke(i,1,num) { // cout<<p[i]<<endl; tot += p[i]; tot %= mod; } write(tot); return 0; }
然而并不知道为什么。。。找了个题解，发现没啥区别，然后就改了一下num的顺序，结果变成80，最神奇的是之前错的那个点对了，然而另两个点错了。。。
#include<iostream> #include<cstdio> #include<cmath> #include<ctime> #include<queue> #include<algorithm> #include<stack> #include<cstring> using namespace std; #define duke(i,a,n) for(int i = a;i <= n;i++) #define lv(i,a,n) for(int i = a;i >= n;i--) #define clean(a) memset(a,0,sizeof(a)) typedef long long ll; const int INF = 1 << 30; const ll mod = 12345678910; typedef double db; template <class T> void read(T &x) { char c; bool op = 0; while(c = getchar(), c < '0' || c > '9') if(c == '-') op = 1; x = c - '0'; while(c = getchar(), c >= '0' && c <= '9') x = x * 10 + c - '0'; if(op) x = -x; } template <class T> void write(T x) { if(x < 0) putchar('-'), x = -x; if(x >= 10) write(x / 10); putchar('0' + x % 10); } ll n,s = 0; ll p[50000],x,ans = 0; ll num = 1; int main() { // freopen("1.in","r",stdin); // freopen("1.out","w",stdout); read(n); p[0] = 0; p[1] = 0; clean(p); duke(i,1,n) { read(x); if(x == 0) { p[num++] = x; } if(x == 1) { s = 0; while (p[num - 1] != 0) { s += p[num - 1]; s = s % mod; num--; } /*if(i == n) { printf("%lld ",s); cout<<num - 1<<endl; }*/ if(s == 0) { p[num - 1] = 1; } else { p[num - 1] = (s * 2) % mod; } /*if(i == n) { printf("%lld ",p[num - 1]); cout<<num - 1<<endl; }*/ } } ll tot = 0; duke(i,1,num - 1) { // cout<<p[i]<<endl; tot += p[i]; tot %= mod; } write(tot); return 0; }
蒙了，然后一点点de,到最后也没看出来。通过一些手段发现了是算和的时候出问题了，然而并不知道为什么。。。
#include<iostream> #include<cstdio> #include<cmath> #include<ctime> #include<queue> #include<algorithm> #include<stack> #include<cstring> using namespace std; #define duke(i,a,n) for(int i = a;i <= n;i++) #define lv(i,a,n) for(int i = a;i >= n;i--) #define clean(a) memset(a,0,sizeof(a)) typedef long long ll; const int INF = 1 << 30; const ll mod = 12345678910; typedef double db; template <class T> void read(T &x) { char c; bool op = 0; while(c = getchar(), c < '0' || c > '9') if(c == '-') op = 1; x = c - '0'; while(c = getchar(), c >= '0' && c <= '9') x = x * 10 + c - '0'; if(op) x = -x; } template <class T> void write(T x) { if(x < 0) putchar('-'), x = -x; if(x >= 10) write(x / 10); putchar('0' + x % 10); } ll n,s = 0; ll p[50000],x,ans = 0; ll num = 1; int main() { // freopen("1.in","r",stdin); // freopen("1.out","w",stdout); read(n); p[0] = 0; p[1] = 0; clean(p); duke(i,1,n) { read(x); if(x == 0) { p[num] = x; num++; } if(x == 1) { s = 0; while (p[num - 1] != 0) { s += p[num - 1]; s = s % mod; num--; } if(s == 0) { p[num - 1] = 1; } else { p[num - 1] = (s * 2) % mod; } } } for(int i=2;i<num;i++) { // cout<<p[i]<<endl; p[1] += p[i]; p[1] = p[1] % 12345678910; } cout<<p[1]; return 0; } /* 6 0 0 1 1 0 1 ( ( ) ) ( ) 0 0 1 2 0 1 */
就是把
ll tot = 0; duke(i,1,num - 1) { // cout<<p[i]<<endl; tot += p[i]; tot %= mod; } write(tot);
换成
for(int i=2;i<num;i++) { // cout<<p[i]<<endl; p[1] += p[i]; p[1] = p[1] % 12345678910; } cout<<p[1];
就对了！！！震惊！！！为什么？求大佬解释。。。