39 lines
824 B
C
39 lines
824 B
C
#include <stdio.h>
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#define MOD 1000000000
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long long dp[101][10];
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int main() {
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for (int i=1; i<10; i++) dp[1][i] = 1;
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int N;
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scanf("%d",&N);
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for (int n=1; n<N; n++) {
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for (int num=0; num<10; num++) {
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if (dp[n][num] == 0) continue;
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int next_num = num - 1;
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if (0<=next_num && next_num <=9) {
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dp[n+1][next_num] += dp[n][num];
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dp[n+1][next_num] %= MOD;
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}
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next_num = num + 1;
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if (0<=next_num && next_num <=9) {
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dp[n+1][next_num] += dp[n][num];
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dp[n+1][next_num] %= MOD;
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}
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}
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}
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long long result = 0;
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for(int i=0; i<10; i++) {
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result += dp[N][i];
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result %= MOD;
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}
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printf("%lld\n",result);
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return 0;
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} |