【模板】KMP
1 int next[N]; 2 char str1[M],str2[N]; 3 //str1 长，str2 短 4 //len1,len2,对应str1,str2的长 5 6 void get_next(int len2) 7 { 8 int i = 0,j = -1; 9 next[0] = -1; 10 while(i<len2) 11 { 12 if(j == -1 || str2[i] == str2[j]) 13 { 14 i++; 15 j++; 16 if(str2[i] != str2[j]) 17 next[i] = j; 18 else 19 next[i] = next[j]; 20 } 21 else 22 j = next[j]; 23 } 24 //计算某字符串的周期，如aaaa是4，abcd是1 25 /* 26 int i = 0;j = -1; 27 next[0] = -1; 28 while(str2[i]) 29 { 30 if(j == -1 || str2[i] == str2[j]) 31 { 32 i++;j++; 33 next[i] = j; 34 } 35 else 36 j = next[j]; 37 } 38 len = strlen(str); 39 i = len-j; 40 if(len%i==0) 41 return len/i; 42 else 43 return 1; 44 */ 45 } 46 47 int kmp(int len1,int len2) 48 { 49 int i = 0,j = 0; 50 get_next(len2); 51 while(i<len1) 52 { 53 if(j == -1 || str1[i] == str2[j]) 54 { 55 i++; 56 j++ 57 } 58 else 59 j = next[j]; 60 /* 61 if(j == len2)//计算str2在str1中出现多少次 62 { 63 cnt++; 64 j= next[j]; 65 } 66 */ 67 } 68 //return j; //j为匹配的长度 69 if(j>len2) 70 return 1;//这里也可以返回i-len2来获得匹配在主串中开始的位置 71 else 72 return 0; 73 } 74 75 //数字KMP 76 int a[1000005],b[10005]; 77 int next[10005],n,m; 78 79 void getnext() 80 { 81 int i = 0,j = -1; 82 next[0] = -1; 83 while(i<m) 84 { 85 if(j == -1 || b[i] == b[j]) 86 { 87 i++; 88 j++; 89 if(b[i] == b[j]) 90 next[i] = next[j]; 91 else 92 next[i] = j; 93 } 94 else 95 j = next[j]; 96 } 97 } 98 99 int kmp()//返回匹配位置 100 { 101 int i = 0,j = 0; 102 while(i<n) 103 { 104 if(a[i] == b[j]) 105 { 106 if(j == m-1) 107 return i-j+1; 108 i++; 109 j++; 110 } 111 else 112 { 113 j = next[j]; 114 if(j == -1) 115 { 116 i++; 117 j = 0; 118 } 119 } 120 } 121 return -1; 122 }