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以前看过,数去数来总算数出了思路#include<stdio.h> #include<string.h> #include<memory.h> long f[26][6]; long g[5]; void INIT() { memset(f,0,sizeof(f)); memset(g,0,sizeof(g)); int i,j,k; for(i=0;i<26;i++) f[i][1]=1; g[1]=26; for(k=2;k<6;k++) for(i=0;i<26;i++) { for(j=i+1;j<26;j++) f[i][k]+=f[j][k-1]; } for(i=2;i<5;i++) for(j=0;j<26;j++) g[i]+=f[j][i]; } bool check(char data[]) { int len=strlen(data); int i,j; for(i=0;i<len;i++) { for(j=i+1;j<len;j++) if(data[i]>=data[j])return false; } return true; } int ans(char data[]) { int len=strlen(data); int i,j; int sum=0; int p; for(i=1;i<len;i++) sum+=g[i]; sum++; for(i=0;i<len;i++) { p=len-i; if(i==0) { for(j=0;j<data[i]-'a';j++) sum+=f[j][p]; } else { for(j=data[i-1]-'a'+1;j<data[i]-'a';j++) sum+=f[j][p]; } } return sum; } int main() { char data[6]; INIT(); while(scanf("%s",&data)!=EOF) { if(!check(data)) printf("0\n"); else { printf("%d\n",ans(data)); } } return 0; } Followed by: Post your reply here: |
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