combinatorics / Extremal graph theory; graph decompositions

The Erdos-Gallai cycle decomposition conjecture (Erdos Problem #184)

Theorem 1.1: an absolute constant CC exists such that the edges of every finite simple graph on nn vertices partition into at most CnCn simple cycles and single edges. Corollary 1.2: every Eulerian graph partitions into at most CnCn cycles, and under a quasirandom cut condition into Δ/2+δn\Delta/2+\delta n cycles. The constant is not computed or optimized; the conjectured sharp values (Erdos suggested n−1n-1; K3,n−3K_{3,n-3}-type lower bounds of about 3n/23n/2) are not addressed.

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combinatoricsSep 24, 2026Significance 40/100Registry: lean checked

The Erdos-Gallai cycle decomposition conjecture (Erdos Problem #184)

Prior state unknown→proved

Theorem 1.1: an absolute constant CC exists such that the edges of every finite simple graph on nn vertices partition into at most CnCn simple cycles and single edges. Corollary 1.2: every Eulerian graph partitions into at most CnCn cycles, and under a quasirandom cut condition into Δ/2+δn\Delta/2+\delta n cycles. The constant is not computed or optimized; the conjectured sharp values (Erdos suggested n−1n-1;…

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Theorem 1.1: an absolute constant CC exists such that the edges of every finite simple graph on nn vertices partition into at most CnCn simple cycles and single edges. Corollary 1.2: every Eulerian graph partitions into at most CnCn cycles, and under a quasirandom cut condition into Δ/2+δn\Delta/2+\delta n cycles. The constant is not computed or optimized; the conjectured sharp values (Erdos suggested n−1n-1; K3,n−3K_{3,n-3}-type lower bounds of about 3n/23n/2) are not addressed.

Theorem 1.1: an absolute constant CC exists such that the edges of every finite simple graph on nn vertices partition into at most CnCn simple cycles and single edges. Corollary 1.2: every Eulerian graph partitions into at most CnCn cycles, and under a quasirandom cut condition into Δ/2+δn\Delta/2+\delta n cycles. The constant is not computed or optimized; the conjectured sharp values (Erdos suggested n−1n-1; K3,n−3K_{3,n-3}-type lower bounds of about 3n/23n/2) are not addressed.

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The Erdos-Gallai cycle decomposition conjecture (Erdos Problem #184) — Mathematical Frontier Network