标签：io ar os sp for div on 2014 art
/**
* @brief Codeforces Round #277 (Div. 2) c
* @file c.c
* @author 面码
* @created 2014/11/14 13:39
* @edited 2014/11/14 13:39
* @type greedy
*
*/
#include <stdio.h>
#define MAXN 100010
#define MAXC 26
#define max(a, b) ((a) > (b) ? (a) : (b))
#define min(a, b) ((a) > (b) ? (b) : (a))
#define abs(a) ((a) > 0 ? (a) : (0 - (a)))
int n, p;
char str[MAXN];
int lft_mv, rht_mv, updown_mv, lft_max, rht_max;
int main(void){
char *lft; /*ptr to left*/
char *rht; /*ptr to right*/
char *idx; /*ptr to start pos*/
char *curr; /*ptr to char wait to convert*/
int dir; /*convert str in right half or left half?*/
int midl, midr;
int ans;
#ifdef DEBUG
freopen("./in", "r", stdin);
freopen("./out", "w", stdout);
#endif
scanf("%d%d%s", &n, &p, str);
p--; /*p start from 0 now*/
midr = n >> 1;
if(n&0x1){
dir = p > midr ? 1: 0;
}else{
midl = midr - 1;
dir = p >= midr ? 1 : 0;
}
#ifdef DEBUG
printf("pos at %s\n", dir ? "right" : "left");
#endif
lft = str;
rht = str + n - 1;
idx = str + p;
lft_max = -1;
rht_max = -1;
updown_mv = 0;
while(lft <= rht){ /*analysis str*/
if(*lft != *rht){
curr = dir ? rht : lft;
if(curr >= idx){
rht_mv = curr - idx;
rht_max = max(rht_max, rht_mv);
}
if(curr <= idx){
lft_mv = idx - curr;
lft_max = max(lft_max, lft_mv);
}
updown_mv += min(abs(*lft - *rht), abs(MAXC - abs(*lft - *rht)));
}
#ifdef DEBUG
printf("rht_max = %d, lft_max = %d, updown_max = %d, lft = %p, rht = %p, idx = %p\n", rht_max, lft_max, updown_mv, lft, rht, idx);
#endif
lft++;
rht--;
}
do{ /**analysis all cases here*/
if(-1 == lft_max && -1 == rht_max){
ans = 0;
break;
}
if(-1 == lft_max){
ans = rht_max + updown_mv;
break;
}
if(-1 == rht_max){
ans = lft_max + updown_mv;
break;
}
ans = (lft_max < rht_max ? (lft_max << 1) + rht_max : (rht_max << 1) + lft_max) + updown_mv;
}while(0);
printf("%d\n", ans);
return 0;
}
Codeforces Round #277 (Div. 2) c
标签：io ar os sp for div on 2014 art
原文地址：http://my.oschina.net/u/572632/blog/344833
