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Java Solution for LeetCode algorithm problems, continually updating
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package g2201_2300.s2266_count_number_of_texts;
// #Medium #String #Hash_Table #Dynamic_Programming #Math
// #2022_06_15_Time_38_ms_(81.43%)_Space_51.2_MB_(80.48%)
@SuppressWarnings("java:S135")
public class Solution {
public int countTexts(String pressedKeys) {
int len = pressedKeys.length();
long dp0 = 1L;
long dp1 = 0;
long dp2 = 0;
long dp3 = 0;
long dp4;
char[] keys = pressedKeys.toCharArray();
int base = 1000000007;
for (int i = 1; i < len; i++) {
int r = keys[i] - '0';
dp4 = dp3;
dp3 = dp2;
dp2 = dp1;
dp1 = dp0 % base;
dp0 = dp1;
dp0 += (i - 1 == 0 && keys[i] == keys[i - 1]) ? 1 : 0;
if (i - 1 <= 0 || keys[i] != keys[i - 1]) {
continue;
}
dp0 += dp2;
dp0 += (i - 2 == 0 && keys[i] == keys[i - 2]) ? 1 : 0;
if (i - 2 <= 0 || keys[i] != keys[i - 2]) {
continue;
}
dp0 += dp3;
dp0 += (i - 3 == 0 && keys[i] == keys[i - 3] && (r == 7 || r == 9)) ? 1 : 0;
if (i - 3 <= 0 || keys[i] != keys[i - 3] || (r != 7 && r != 9)) {
continue;
}
dp0 += dp4;
}
return (int) (dp0 % base);
}
}