2015 Multi-University Training Contest 7 hdu 5375 Gray code

Gray code

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 129 Accepted Submission(s): 68


[align=left]Problem Description[/align]
The reflected binary code, also known as Gray code after Frank Gray, is a binary numeral system where two successive values differ in only onebit (binary digit). The reflected binary code was originally designed to prevent spurious output from electromechanical switches. Today, Gray codes are widely used to facilitate error correction in digital communications such as digital terrestrial television and some cable TV systems.

#include <bits/stdc++.h>
using namespace std;
const int maxn = 210010;
int dp[maxn][2],w[maxn],len;
char str[maxn];
int main() {
int kase,cs = 1;
scanf("%d",&kase);
while(kase--) {
scanf("%s",str);
len = strlen(str);
for(int i = 0; i < len; ++i)
scanf("%d",w + i);
memset(dp,-1,sizeof dp);
if(str[0] == '0' || str[0] == '?') dp[0][0] = 0;
if(str[0] == '1' || str[0] == '?') dp[0][1] = w[0];
for(int i = 1; i < len; ++i){
if(str[i] == '1' || str[i] == '?'){
if(dp[i-1][1] != -1) dp[i][1] = max(dp[i][1],dp[i-1][1]);
if(dp[i-1][0] != -1) dp[i][1] = max(dp[i][1],dp[i-1][0] + w[i]);
}
if(str[i] == '0' || str[i] == '?'){
if(dp[i-1][0] != -1) dp[i][0] = max(dp[i][0],dp[i-1][0]);
if(dp[i-1][1] != -1) dp[i][0] = max(dp[i][0],dp[i-1][1] + w[i]);
}
}
printf("Case #%d: %d\n",cs++,max(dp[len-1][0],dp[len-1][1]));
}
return 0;
}

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