Palindrome
As an example, by inserting 2 characters, the string “Ab3bd” can be transformed into a palindrome (“dAb3bAd” or “Adb3bdA”). However, inserting fewer than 2 characters does not produce a palindrome.
题目大意:输入一个数字,代表字符串的长度,输入一个字符串,判断最少插入多少个字符能使其变为回文串(正序与反序相同)。
题解代码:
#include
#include
#define Max(a,b) a>b?a:b int main() {
int i,j,n,dp[2][5005]; char str[5005],str2[5005]; while(~scanf("%d",&n)) {
getchar(); gets(str); memset(dp,0,sizeof(dp)); for(i = 0,j = n-1; str[i]!='\0'; i++,j--) {
str2[i] = str[j]; } for(i = 0; str[i]!='\0'; i++) {
for(j = 0; str2[j]!='\0'; j++) {
if(str[i] == str2[j]) {
dp[(i+1)%2][j+1] = dp[i%2][j]+1; } else {
dp[(i+1)%2][j+1] = Max(dp[i%2][j+1],dp[(i+1)%2][j]); } } } printf("%d\n",n-dp[n%2][n]); } return 0; }
hncu2021acm1—1005
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