先打上代码以后更新解释
1 #include <cstdio> 2 #include <iostream> 3 #include <algorithm> 4 #include <cstring> 5 #include <cmath> 6 #define REP(i, s, n) for(int i = s; i <= n; i ++) 7 #define RAP(i, n, s) for(int i = n; i >= s; i --) 8 #define LOW for(; x; x -= x & (-x)) 9 using namespace std; 10 const int maxn = 100000 + 10; 11 const int Maxn = 100000; 12 const int maxnode = 200 * maxn; 13 int s[maxnode], ls[maxnode], rs[maxnode], A[maxn], root[maxn], Ln, Rn, L[maxn], R[maxn], c[maxn]; 14 int n, Q, ms = 0; 15 void update(int x, int& y, int L, int R, int pos, int v){ 16 s[y = ++ ms] = s[x] + v; 17 if(L == R) return ; 18 int M = L + R >> 1; 19 ls[y] = ls[x]; rs[y] = rs[x]; 20 if(pos <= M) update(ls[x], ls[y], L, M, pos, v); 21 else update(rs[x], rs[y], M + 1, R, pos, v); 22 return ; 23 } 24 void update(int x, int v){ 25 for(int i = x; i <= Maxn; i += i & (-i)) update(c[i], c[i], 1, Maxn, A[x], -1); A[x] = v; 26 for(int i = x; i <= Maxn; i += i & (-i)) update(c[i], c[i], 1, Maxn, A[x], 1); return ; 27 } 28 void init(int x, int tp){ 29 if(!tp) { L[++ Ln] = root[x]; LOW if(c[x]) L[++ Ln] = c[x]; } 30 else { R[++ Rn] = root[x]; LOW if(c[x]) R[++ Rn] = c[x]; } 31 return ; 32 } 33 int query(int ql, int qr, int k){ 34 Ln = Rn = 0; init(qr, 1); init(ql - 1, 0);//0是左 35 int ll = 1, rr = Maxn; 36 while(ll < rr){ 37 int Lsum = 0, Rsum = 0, M = ll + rr >> 1; 38 REP(i, 1, Ln) Lsum += s[ls[L[i]]]; 39 REP(i, 1, Rn) Rsum += s[ls[R[i]]]; 40 int kth = Rsum - Lsum; 41 if(kth >= k){//往左找 42 REP(i, 1, Ln) L[i] = ls[L[i]]; 43 REP(i, 1, Rn) R[i] = ls[R[i]]; 44 rr = M; 45 } 46 else{//往右找 47 REP(i, 1, Ln) L[i] = rs[L[i]]; 48 REP(i, 1, Rn) R[i] = rs[R[i]]; 49 ll = M + 1; k -= kth; //看好了二分！ 别忘了还要减 Σ( ° △ °|||)︴ 50 } 51 } 52 return ll; 53 } 54 inline void read(int &x){ 55 x = 0; int sig = 1; char ch = getchar(); 56 while(!isdigit(ch)) { if(ch == '-') sig = -1; ch = getchar(); } 57 while(isdigit(ch)) x = 10 * x + ch - '0', ch = getchar(); 58 x *= sig; return ; 59 } 60 inline void write(int x){ 61 if(x == 0) { putchar('0'); return ; } 62 if(x < 0) putchar('-'), x = -x; 63 int len = 0, buf[20]; 64 while(x) buf[len ++] = x % 10, x /= 10; 65 RAP(i, len - 1, 0) putchar(buf[i] + '0'); return ; 66 } 67 void init(){ 68 read(n); read(Q); 69 REP(i, 1, n) read(A[i]); 70 REP(i, 1, n) update(root[i - 1], root[i], 1, Maxn, A[i], 1); 71 return ; 72 } 73 void work(){ 74 int tp, ql, qr, k, x, v; 75 while(Q --){ 76 read(tp); 77 if(tp) read(ql), read(qr), read(k), write(query(ql, qr, k) - 1), putchar(' ');// 减一 78 else read(x), read(v), update(x, v); 79 } 80 return ; 81 } 82 void print(){ 83 84 return ; 85 } 86 int main(){ 87 init(); 88 work(); 89 print(); 90 return 0; 91 }
逗比版：
1 #include<iostream> 2 #include<cstdio> 3 #include<cmath> 4 #include<algorithm> 5 #define t node[d] 6 #define cnt countn[d] 7 #define repnode(d) for(int i=1;i<=countn[d];i++) 8 using namespace std; 9 const int maxn=100000+10,maxnode=20000000+10,Max=100000; 10 int ls[maxnode],rs[maxnode],s[maxnode],root[maxn],A[maxn],c[maxn],n,m,ms=0,countn[2],node[2][maxn],sum[2]; 11 void update(int x,int& y,int L,int R,int pos,int d){ 12 s[y=++ms]=s[x]+d; 13 if(L==R) return; 14 ls[y]=ls[x];rs[y]=rs[x]; 15 int M=L+R>>1; 16 if(pos<=M) update(ls[x],ls[y],L,M,pos,d); 17 else update(rs[x],rs[y],M+1,R,pos,d); 18 return; 19 } 20 void update(int x,int v){ 21 for(int i=x;i<=Max;i+=i&-i) update(c[i],c[i],1,Max,A[x],-1);A[x]=v; 22 for(int i=x;i<=Max;i+=i&-i) update(c[i],c[i],1,Max,A[x],1);return; 23 } 24 void init(int x,int d){ 25 t[++cnt]=root[x]; 26 for(;x;x-=x&-x) if(c[x]) t[++cnt]=c[x]; 27 return; 28 } 29 int query(int ql,int qr,int k){ 30 countn[0]=countn[1]=0; 31 init(qr,1);init(ql-1,0); 32 int L=1,R=Max,d; 33 while(L<R){ 34 sum[0]=sum[1]=0; 35 int M=L+R>>1; 36 repnode(d=0) sum[d]+=s[ls[t[i]]]; 37 repnode(d=1) sum[d]+=s[ls[t[i]]]; 38 int kth=sum[1]-sum[0]; 39 if(k<=kth){ 40 repnode(d=0) t[i]=ls[t[i]]; 41 repnode(d=1) t[i]=ls[t[i]]; 42 R=M; 43 } 44 else{ 45 repnode(d=0) t[i]=rs[t[i]]; 46 repnode(d=1) t[i]=rs[t[i]]; 47 L=M+1;k-=kth; 48 } 49 } return L; 50 } 51 inline int read(){ 52 int x=0,sig=1;char ch=getchar(); 53 while(!isdigit(ch)){if(ch=='-') sig=-1;ch=getchar();} 54 while(isdigit(ch)) x=10*x+ch-'0',ch=getchar(); 55 return x*=sig; 56 } 57 inline void write(int x){ 58 if(x==0){putchar('0');return;} if(x<0) putchar('-'),x=-x; 59 int len=0,buf[15]; while(x) buf[len++]=x%10,x/=10; 60 for(int i=len-1;i>=0;i--) putchar(buf[i]+'0');return; 61 } 62 void init(){ 63 n=read();m=read(); 64 for(int i=1;i<=n;i++) A[i]=read(); 65 for(int i=1;i<=n;i++) update(root[i-1],root[i],1,Max,A[i],1); 66 return; 67 } 68 void work(){ 69 int tp,i,j,k,x,v; 70 while(m--){ 71 tp=read(); 72 if(tp){ 73 i=read();j=read();k=read(); 74 write(query(i,j,k)-1);putchar(' '); 75 } 76 else{ 77 x=read();v=read(); 78 update(x,v); 79 } 80 } 81 return; 82 } 83 void print(){ 84 return; 85 } 86 int main(){ 87 init();work();print();return 0; 88 }